DOCS: Unpin pydata-sphinx-theme

[lithomas1]

The pydata-sphinx-theme has a new release, and that causes some issues with the top bar:

So we can maybe temporarily pin the theme until that is fixed

from #55159

[hkhojasteh]

@jorisvandenbossche I guess this is going to be fixed straightforwardly by changing the top bar search column style in the new theme version. It is similar to yesterday's sprint fix. So I will gladly take care of it.
@lithomas1 or shall we wait for the fix from pydata-sphinx-theme slide?