Added docs to fix GL08 errors in CustomBusinessHours
- [ ] xref #27977
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Currently even after adding the docstrings the command `python scripts/validate_docstrings.py --errors=GL08` does not pick up the changes.