DOC: Fix docstring title sections
Changed "See also" section titles to "See Also" to fit with the new validator

- [x] closes #23640 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @gueletk! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/accessor.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/accessor.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/categorical.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/arrays/categorical.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimes.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/arrays/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/period.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/arrays/period.py) !

 - There are no PEP8 issues in the file [`pandas/core/base.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/frame.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/frame.py) !

 - There are no PEP8 issues in the file [`pandas/core/generic.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/generic.py) !

 - There are no PEP8 issues in the file [`pandas/core/groupby/generic.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/groupby/generic.py) !

 - There are no PEP8 issues in the file [`pandas/core/groupby/groupby.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/groupby/groupby.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/base.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/indexes/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/datetimelike.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/indexes/datetimelike.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/multi.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/indexes/multi.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/numeric.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/indexes/numeric.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/range.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/indexes/range.py) !

 - There are no PEP8 issues in the file [`pandas/core/ops.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/ops.py) !

 - There are no PEP8 issues in the file [`pandas/core/resample.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/resample.py) !

 - There are no PEP8 issues in the file [`pandas/core/reshape/merge.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/reshape/merge.py) !

 - There are no PEP8 issues in the file [`pandas/core/reshape/util.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/reshape/util.py) !

 - There are no PEP8 issues in the file [`pandas/core/series.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/series.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/datetimes.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/tools/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/numeric.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/tools/numeric.py) !

 - There are no PEP8 issues in the file [`pandas/core/tools/timedeltas.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/tools/timedeltas.py) !

 - There are no PEP8 issues in the file [`pandas/core/window.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/core/window.py) !

 - There are no PEP8 issues in the file [`pandas/io/json/table_schema.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/io/json/table_schema.py) !

 - There are no PEP8 issues in the file [`pandas/io/sql.py`](https://github.com/gueletk/pandas/blob/e473278c68e31b96729343720e0f385c7bd1da23/pandas/io/sql.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=h1) Report
> Merging [#23653](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a08bf3de02bb1e53fb95df24ae060b63c2a44c96?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23653/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23653   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         161      161           
  Lines       51317    51317           
=======================================
  Hits        47338    47338           
  Misses       3979     3979
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <ø> (ø)` | :arrow_up: |
| #single | `42.31% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/tools/numeric.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvbnVtZXJpYy5weQ==) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/io/json/table\_schema.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vdGFibGVfc2NoZW1hLnB5) | `98.29% <ø> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `95.46% <ø> (ø)` | :arrow_up: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `97.61% <ø> (ø)` | :arrow_up: |
| [pandas/core/tools/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvdGltZWRlbHRhcy5weQ==) | `98.03% <ø> (ø)` | :arrow_up: |
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `96.99% <ø> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `98.44% <ø> (ø)` | :arrow_up: |
| [pandas/core/window.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvd2luZG93LnB5) | `96.4% <ø> (ø)` | :arrow_up: |
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `94.25% <ø> (ø)` | :arrow_up: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.34% <ø> (ø)` | :arrow_up: |
| ... and [14 more](https://codecov.io/gh/pandas-dev/pandas/pull/23653/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=footer). Last update [a08bf3d...e473278](https://codecov.io/gh/pandas-dev/pandas/pull/23653?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
