Modification of validate_rst_title_capitalization.py script
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @cleconte987! Thanks for opening this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

* In the file [`scripts/validate_rst_title_capitalization.py`](https://github.com/pandas-dev/pandas/blob/048fb783f299d3238dbe113744fa2d20b12ec3c3/scripts/validate_rst_title_capitalization.py):

> [Line 77:5](https://github.com/pandas-dev/pandas/blob/048fb783f299d3238dbe113744fa2d20b12ec3c3/scripts/validate_rst_title_capitalization.py#L77): [E265](https://duckduckgo.com/?q=pep8%20E265) block comment should start with '# '
> [Line 77:65](https://github.com/pandas-dev/pandas/blob/048fb783f299d3238dbe113744fa2d20b12ec3c3/scripts/validate_rst_title_capitalization.py#L77): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 78:5](https://github.com/pandas-dev/pandas/blob/048fb783f299d3238dbe113744fa2d20b12ec3c3/scripts/validate_rst_title_capitalization.py#L78): [E265](https://duckduckgo.com/?q=pep8%20E265) block comment should start with '# '
> [Line 79:5](https://github.com/pandas-dev/pandas/blob/048fb783f299d3238dbe113744fa2d20b12ec3c3/scripts/validate_rst_title_capitalization.py#L79): [E265](https://duckduckgo.com/?q=pep8%20E265) block comment should start with '# '

