Don't report missing packages on apt for packages no longer in an active Apertis release

Dashboard goes through all the packages in GitLab and reports
an error if they are not published in apt repositories. Unfortunately,
this behavior does not take into account the fact that packages can
be dropped in a release, so they are no longer published.
To fix that, don't report missing packages on apt for packages no
longer in an active Apertis release.

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