DOC: Updated docstrings related to DateTimeIndex. GH22459
- [ ] closes #xxxx
- [x] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Updated `pandas.date_range` and `pandas.bdate_range` docstrings to resolve errors raised from `scripts/validate_docstrings.py` from #22459. Also added an example to `pandas.bdate_range`.