DOC: Fix SA01 Docstring Errors for DataFrame
- [ ] xref #58065

Fixed SA01 issues for the following methods:

`pandas.DataFrame.__iter__`
`pandas.DataFrame.columns`
`pandas.DataFrame.droplevel`

Fixed functions also removed from code_checks.sh
Thanks @gboeker 

(Note: if your PR doesn't completely close the linked issue, could you replace `closes` with `xref` next time)