TST (string dtype): follow-up on GH-59329 fixing new xfails
Follow-up on https://github.com/pandas-dev/pandas/pull/59329, which caused some failures on main after being merged (see https://github.com/pandas-dev/pandas/pull/59329#issuecomment-2258200402)


xref https://github.com/pandas-dev/pandas/issues/54792
The build (for future strings) is green again. I think it would be good to merge this rather quickly given it's fixing failures on main (will do in a few hours if no-one beats me to it). Thanks @jorisvandenbossche 