TST: add error message match for raise in test_datetimelike.py GH30999
Reference #30999

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

lgtm. @MarcoGorelli merge when ready. Thanks @liaoaoyuan97 !