DOC: Fixes flake8 issues in whatsnew v0.13.* #24256
- [ ] closes #24256 


I am not sure if there is anything different I can do with the merge conflict in setup.cfg.  Please advise. pls merge master # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=h1) Report
> Merging [#24322](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3675c29a7bf8714d3f83d1c6a854325702f81969?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/24322/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24322      +/-   ##
==========================================
- Coverage   92.28%   92.28%   -0.01%     
==========================================
  Files         162      162              
  Lines       51831    51835       +4     
==========================================
+ Hits        47833    47835       +2     
- Misses       3998     4000       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.68% <ø> (-0.01%)` | :arrow_down: |
| #single | `43% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/\_test\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3RfZGVjb3JhdG9ycy5weQ==) | `90.54% <0%> (-2.71%)` | :arrow_down: |
| [pandas/core/indexes/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9wZXJpb2QucHk=) | `93.09% <0%> (+0.03%)` | :arrow_up: |
| [pandas/core/reshape/tile.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS90aWxlLnB5) | `94.82% <0%> (+0.06%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24322?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/24322?src=pr&el=footer). Last update [3675c29...70f5b2e](https://codecov.io/gh/pandas-dev/pandas/pull/24322?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/24322?src=pr&el=h1) Report
> Merging [#24322](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3675c29a7bf8714d3f83d1c6a854325702f81969?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/24322/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24322      +/-   ##
==========================================
- Coverage   92.28%   92.28%   -0.01%     
==========================================
  Files         162      162              
  Lines       51831    51835       +4     
==========================================
+ Hits        47833    47835       +2     
- Misses       3998     4000       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.68% <ø> (-0.01%)` | :arrow_down: |
| #single | `43% <ø> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/\_test\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3RfZGVjb3JhdG9ycy5weQ==) | `90.54% <0%> (-2.71%)` | :arrow_down: |
| [pandas/core/indexes/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9wZXJpb2QucHk=) | `93.09% <0%> (+0.03%)` | :arrow_up: |
| [pandas/core/reshape/tile.py](https://codecov.io/gh/pandas-dev/pandas/pull/24322/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS90aWxlLnB5) | `94.82% <0%> (+0.06%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24322?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/24322?src=pr&el=footer). Last update [3675c29...1a2a225](https://codecov.io/gh/pandas-dev/pandas/pull/24322?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @Seuss27 