Drop generated man pages from git, let distro packages generate them

[Bastian-Krause]

sphinx is fast to remove support for still supported Python versions. That means we will probably always have differing output depending on the various sphinx/docutils versions compatible with each Python version we support. That problem won't go away.

That's why I think we should move away from tracking the generated man pages in git. Instead the distro packaging should generate them using distro packages of sphinx/sphinxcontrib-autoprogram.

Originally posted by @Bastian-Krause in #1802 (comment)

We should add that to our Debian packaging exemplarily.