Revert "Deprecate text.latex.unicode." - #11345

I'm almost certain that #11292 would fix the issue (per "Use matplotlib.style.context to restore the style at exit, as it relies on rc_context which is ultimately more efficient than rcParams.update as it skips revalidation"). Triggering a rebuild of that PR now to check.

Sorry for the disturbance.

I'm going to merge this since it will get rid of all the messages for now, sorry for not checking and merging the original PR.

I put back a better(?) version in https://github.com/matplotlib/matplotlib/pull/11381/files, would be nice to know how it is causing problems in holoviews (can you provide a repro?).
It's still in rcsetup.py given that, yes, we want people to still be able to access it but have access trigger a deprecation.