CLN: Removed outdated comment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

I think this is a bit outdated, since we are using black and it's doing the work for us, right?

according to git blame, this is 2 years old.