CI: Fix Failing Doc Build
https://github.com/pandas-dev/pandas/pull/43145 had failing code checks

https://github.com/pandas-dev/pandas/pull/43347/checks?check_run_id=3488498926

```
/home/runner/work/pandas/pandas/doc/source/whatsnew/v1.3.3.rst:36: WARNING: Bullet list ends without a blank line; unexpected unindent.
```