TST (string dtype): fix xfails in test_algos.py
Remaining xfails in `test_algos.py`

xref https://github.com/pandas-dev/pandas/issues/54792
Does #59433 cover this? Ah, sorry, should have checked the open PRs first. Will put that on my to do list to review (for next week) Covered by https://github.com/pandas-dev/pandas/pull/59433, so closing this PR.