po: rename the .mini.po files to have just a .po suffix

po: rename the .mini.po files to have just a .po suffix

A .mini.po file is exactly the same format as a .po file. We just used
the alternative extension as we wanted to be able to store both full and
minimized forms in the same directory.

This complicates integration with some translation tools, however, which
only really expect to see $LANG.po as a filename.

With this change we drop the rules for creating non-minimized po files,
and thus the po/*.po are always minimized. A useful side effect is that
we no longer run msgmerge during creation of the gmo files, and thus
don't need to have a date override to get reproducible builds.

Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>