docs: Move libX11 / PyQt stuff to "former quirks"

[geofft]

This has been working fine since May 2022....

[geofft]

Honestly we should think about getting rid of the quirks page entirely - the remaining quirks are

• if you're on an unusual OS, we won't be able to find your terminfo
• We don't ship Tix, which is deprecated in all our versions and gone on Python 3.13.
• We don't ship a pip.exe on Windows and you have to use python -m pip (or, like, uv)
• If you're using libpython.a (which isn't in the install-only tarball) on macOS, it's a little complicated
• We use libedit and other people use readline (I think this is barely noticeable with pyrepl)
• Sometimes you will see build-time paths in places that are hopefully harmless