DOC: Update series apply docstring. GH22459
- [X] refs #22459
- [x] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Updated `Series.apply` docstring to resolve errors raised from scripts/validate_docstrings.py from #22459.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=h1) Report
> Merging [#22510](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f2839fe813391140a1e08d3c5f71c04bbaf5ab56?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/22510/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22510   +/-   ##
=======================================
  Coverage   92.29%   92.29%           
=======================================
  Files         161      161           
  Lines       51498    51498           
=======================================
  Hits        47530    47530           
  Misses       3968     3968
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.69% <ø> (ø)` | :arrow_up: |
| #single | `42.43% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/22510/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.68% <ø> (ø)` | :arrow_up: |

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[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=footer). Last update [f2839fe...d5c13b2](https://codecov.io/gh/pandas-dev/pandas/pull/22510?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @datapythonista I removed the type from the **kwds parameter. I also agree that it should be renamed to **kwargs to be more consistent with the rest of the code base.  Hello @eldritchideen! Thanks for updating the PR.



Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on September 04, 2018 at 10:56 Hours UTC I have updated the Series.apply docstring based on review feedback. Thanks @datapythonista and @gfyoung  @eldritchideen do you have time to update this PR based on the comments? @datapythonista I see the self assignment on this - are you actually working this one?  I forgot about it, but fixed the pending issues now. Can you take a look and merge if everything is ok (or fix any outstanding issue, as the PR is discontinued)? thanks @eldritchideen 