DOC: Fixing more doc warnings
Follow up of #24430. Fixing some more doc warnings.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=h1) Report
> Merging [#24431](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/bf31c045ce45cd1b6f85be3d1fbbe7dd40c5a854?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24431/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24431      +/-   ##
==========================================
- Coverage    92.3%    92.3%   -0.01%     
==========================================
  Files         163      163              
  Lines       51978    51977       -1     
==========================================
- Hits        47980    47979       -1     
  Misses       3998     3998
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.71% <ø> (-0.01%)` | :arrow_down: |
| #single | `42.99% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24431/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.62% <ø> (ø)` | :arrow_up: |
| [pandas/core/indexes/accessors.py](https://codecov.io/gh/pandas-dev/pandas/pull/24431/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9hY2Nlc3NvcnMucHk=) | `91% <0%> (-0.09%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24431?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/24431?src=pr&el=footer). Last update [bf31c04...f79efee](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=h1) Report
> Merging [#24431](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/bf31c045ce45cd1b6f85be3d1fbbe7dd40c5a854?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24431/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24431      +/-   ##
==========================================
- Coverage    92.3%    92.3%   -0.01%     
==========================================
  Files         163      163              
  Lines       51978    51977       -1     
==========================================
- Hits        47980    47979       -1     
  Misses       3998     3998
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.71% <ø> (-0.01%)` | :arrow_down: |
| #single | `42.99% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/24431/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.62% <ø> (ø)` | :arrow_up: |
| [pandas/core/indexes/accessors.py](https://codecov.io/gh/pandas-dev/pandas/pull/24431/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9hY2Nlc3NvcnMucHk=) | `91% <0%> (-0.09%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24431?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/24431?src=pr&el=footer). Last update [bf31c04...f79efee](https://codecov.io/gh/pandas-dev/pandas/pull/24431?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!