apertis-pkg-pull-updates: pull updates from *-updates repositories

Updates from *-proposed-updates repositories are not pulled anymore
by default because it can contain undesirable updates for Apertis.
However, we still want updates from *-updates repositories instead.

"proposed-updates" contains updates not officialy part of Debian
contrary to "updates".

Signed-off-by: Dylan Aïssi <dylan.aissi@collabora.com>