Revert change to comparison op with datetime.date objects
- [x] closes #21152
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

cc @jbrockmendel, @innominate227

FYI, @jorisvandenbossche the whatsnew will conflict with your other PR