DOC: Small whatsnew fixes
A few small things that I saw when scanning over the What's New page.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=h1) Report
> Merging [#24738](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/fdc4db25a9988a7b595a3756760d05a6c177123d?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/24738/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24738      +/-   ##
==========================================
- Coverage   92.39%   92.38%   -0.01%     
==========================================
  Files         166      166              
  Lines       52358    52358              
==========================================
- Hits        48374    48373       -1     
- Misses       3984     3985       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <ø> (ø)` | :arrow_up: |
| #single | `43.07% <ø> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24738/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24738?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/24738?src=pr&el=footer). Last update [fdc4db2...20b7b8a](https://codecov.io/gh/pandas-dev/pandas/pull/24738?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/24738?src=pr&el=h1) Report
> Merging [#24738](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/fdc4db25a9988a7b595a3756760d05a6c177123d?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/24738/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24738      +/-   ##
==========================================
- Coverage   92.39%   92.38%   -0.01%     
==========================================
  Files         166      166              
  Lines       52358    52358              
==========================================
- Hits        48374    48373       -1     
- Misses       3984     3985       +1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.81% <ø> (ø)` | :arrow_up: |
| #single | `43.07% <ø> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24738/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24738?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/24738?src=pr&el=footer). Last update [fdc4db2...20b7b8a](https://codecov.io/gh/pandas-dev/pandas/pull/24738?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks!