ci: Remove packages convenience job
The packages we build in CI are now big enough that they can't be
uploaded as a single artifact bundle (which has a size limit on
GitLab.com). This affects the packages job which only exists to make
all the packages easy to access in one job artifacts list.
Avoid this limit for now by leaving the artifacts split across the
mvn package and macos signed packages jobs, where the packages are
actually generated. These jobs seem to be OK at least for now.
This hotfixes the failing CI on the main branch.