Don't allow the `package-and-qa` job to fail

From https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/10327#note_154215462:

I think we should not allow this job to fail since it's manually started, it's confusing to allow it to fail. 🤔

@sliaquat also agrees on that:

Agree to this and now that we have more stable QA tests makes a more compelling case to not allowing it to fail.