Drop man page from the repo

Drop man page from the repo

Let's just generate it on demand with pandoc when needed instead of
storing it in the repo. I initially pushed for putting in the repo
because the mkosi AUR package pulled in hundreds of Haskell dependencies
for pandoc when installing mkosi to build the manpage, but that's an
Arch issue and not something to solve in mkosi. Also, mkosi moved
from the AUR to the community repo these days so it's not an issue
on Arch anymore either.