TST: Update test in #28798 to use a Categorical
- [x] xref #28798
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I merged #28798 too fast, as the column "Name" wasn't a Categorical, which was to be tested. I've made it a Categorical and for good measure I've added ``ordered_fixture`` to the test.