DOC: Improve docs (GH19312) for Series.nonzero()
- [x] closes #19312 
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19324?src=pr&el=h1) Report
> Merging [#19324](https://codecov.io/gh/pandas-dev/pandas/pull/19324?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6ba65ca8a69560d526762bdbded64b3139f66d7a?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19324/graphs/tree.svg?width=650&height=150&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/19324?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19324      +/-   ##
==========================================
- Coverage   91.57%   91.54%   -0.03%     
==========================================
  Files         150      150              
  Lines       48700    48700              
==========================================
- Hits        44595    44583      -12     
- Misses       4105     4117      +12
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.91% <100%> (-0.03%)` | :arrow_down: |
| #single | `41.72% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19324?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/19324/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.6% <100%> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/19324/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.22% <0%> (-1.74%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19324?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/19324?src=pr&el=footer). Last update [6ba65ca...75e2ee4](https://codecov.io/gh/pandas-dev/pandas/pull/19324?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jreback I have updated the PR thanks @drorata 