DOC/CLN: small whatsnew fixes
Small edits to fix some instances where the text isn't rendering as intended.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22659?src=pr&el=h1) Report
> Merging [#22659](https://codecov.io/gh/pandas-dev/pandas/pull/22659?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/0976e1261781153603064eb67d66630a099edcd7?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/22659/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22659?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22659   +/-   ##
=======================================
  Coverage   92.17%   92.17%           
=======================================
  Files         169      169           
  Lines       50708    50708           
=======================================
  Hits        46740    46740           
  Misses       3968     3968
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.58% <ø> (ø)` | :arrow_up: |
| #single | `42.35% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22659?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/22659?src=pr&el=footer). Last update [0976e12...08eba3a](https://codecov.io/gh/pandas-dev/pandas/pull/22659?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
