Remove all links to mingw.org (GH-24552)

Remove all links to mingw.org (GH-24552)

This lease on this domain has lapsed. This not only makes these dead links, but a potential attack vector for readers of python.org as the domain can be obtained by an untrustworthy party.

I considered redirecting these links to http://mingw-w64.org/ which is a maintained fork of mingw, but beyond my unfamiliarity with the exact level of compatibility, at the time of this PR that site had an expired cert and so is not much of a vulnerability fix.

Automerge-Triggered-By: GH:Mariatta