DOC: Updating Series.agg docstring
With reference to: #22459. I have fixed up the agg/map doc strings for `pandas/core/series.py` so they now pass our doc tests. CC @jorisvandenbossche

Thanks,

Thanks for the PR! 
Just a question, how does this fix the `map` docstring? (I only see changes to the agg docstring? Or that one was already passing?) # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22474?src=pr&el=h1) Report
> Merging [#22474](https://codecov.io/gh/pandas-dev/pandas/pull/22474?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/2be2ba570453ab09f0c8da46dfd8e1a179771fee?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/22474/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/22474?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22474   +/-   ##
=======================================
  Coverage   92.04%   92.04%           
=======================================
  Files         169      169           
  Lines       50740    50740           
=======================================
  Hits        46705    46705           
  Misses       4035     4035
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.45% <ø> (ø)` | :arrow_up: |
| #single | `42.24% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22474?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/22474/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.73% <ø> (ø)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/22474/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.44% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22474?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/22474?src=pr&el=footer). Last update [2be2ba5...fd81518](https://codecov.io/gh/pandas-dev/pandas/pull/22474?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks both for the comments. Yes @jorisvandenbossche map doc string was already passing. @datapythonista update as per your comments, let me know if there is anything else, thanks The failure on travis is an unrelated build issue (and already happening on master as well), so merging

Thanks a lot @alimcmaster1 ! Thanks both!! 