Roll back threadsafety workarounds for f2py versions where it's fixed

[pv]

This is reminder to roll back the workaround in gh-12319 (see also gh-9658; possibly there are also other threadsafety workarounds) in some way, if Scipy is compiled with f2py versions where the bug is not present.

The complication with adding Numpy version checks here is that we'd need to check the version of Numpy used to compile Scipy, not the currently imported one. Not sure if that information is stored somewhere. Because of the ABI compatibility stuff, the former is in practice going to often be quite old Numpy, so the f2py fixes won't come in soon. We perhaps should consider for the wheel builds upgrading f2py separately.