[PRQ#67247] Deletion Request for python-pymc3

MarsSeed [1] filed a deletion request for python-pymc3 [2]: EOL v3 version of pymc [a], which is at v5.x. Only officially supports up to Python 3.9. Tests would fail, but they are disabled in this PKGBUID. This library no longer has any reverse dependencies, so it's safe to delete. (Last PKGBUILD to use this, as a checkdepend, was the deprecated python-aesara-theano-fallback, which got deleted via PRQ#66340). [a]: https://pypi.org/project/pymc [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/python-pymc3/