DOC: Fixed table formatting in box plot section
[DOC]fixed table formatting in the box plot section keeing simple rst table format

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

Also @pvanhauw can you update the title of the PR to `[DOC]fixed table formatting in the box plot section`? > Also @pvanhauw can you update the title of the PR to `[DOC]fixed table formatting in the box plot section`?

I  just did  @pvanhauw it seems the PR title rename didn't come through thanks for helping me on my first PR !
