This change updates the copyright year in the `debian/copyright` file
as well as the `Standards-Version` to 4.7.3 in `debian/control`.
Cherry-pick-of: #15558
Test-bot: skip
Also improve upload script to force push changelog branches.
Lintian v2.115 (which is run on Debian servers) still produces
pedantic warnings, but there seems to be a bug - no matter what
pattern I add to `lintian-overrides`, I can't get it to ignore
the files. The following version v2.116 has these rules built in,
so we don't need `lintian-overrides` anymore.
(cherry picked from commit 134e084b80)
