DOC: Fix PR09 errors in several files
- [x] closes #36764
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

As far as I can see, there are some PR09 pandas docstring errors. So with this PR I will resolve them. There are more commits soon.
```
PR09
Parameter description should finish with "."
```