BUG: fix reducing numpy ufuncs for Series/Index
closes #23312

Hello @jorisvandenbossche! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/indexes/base.py`](https://github.com/jorisvandenbossche/pandas/blob/a6cb690694a459fb8bb1c137ee541024ddfa413d/pandas/core/indexes/base.py) !

 - There are no PEP8 issues in the file [`pandas/core/series.py`](https://github.com/jorisvandenbossche/pandas/blob/a6cb690694a459fb8bb1c137ee541024ddfa413d/pandas/core/series.py) !

 - There are no PEP8 issues in the file [`pandas/tests/arithmetic/test_numeric.py`](https://github.com/jorisvandenbossche/pandas/blob/a6cb690694a459fb8bb1c137ee541024ddfa413d/pandas/tests/arithmetic/test_numeric.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23314?src=pr&el=h1) Report
> Merging [#23314](https://codecov.io/gh/pandas-dev/pandas/pull/23314?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/437f31cb609372f465aaa853bf4b2299a9550716?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23314/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23314?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23314      +/-   ##
==========================================
+ Coverage   92.22%   92.22%   +<.01%     
==========================================
  Files         169      169              
  Lines       51258    51263       +5     
==========================================
+ Hits        47274    47279       +5     
  Misses       3984     3984
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.66% <100%> (ø)` | :arrow_up: |
| #single | `42.23% <33.33%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23314?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/23314/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.92% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/23314/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.61% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/sparse.py](https://codecov.io/gh/pandas-dev/pandas/pull/23314/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3NwYXJzZS5weQ==) | `91.84% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23314/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.46% <0%> (ø)` | :arrow_up: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/23314/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `89.28% <0%> (+0.05%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23314?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/23314?src=pr&el=footer). Last update [437f31c...733d027](https://codecov.io/gh/pandas-dev/pandas/pull/23314?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 needs a rebase @jorisvandenbossche can you merge master and update can you merge master (and move notes to 0.25) / or close if going to handle in ``__array_ufunc__``