Update changelog generator to accept new labels

Overview

The ~backstage label was deprecated in gitlab-com/www-gitlab-com!53571 (diffs) we now have 4 new labels:

• featureaddition
• ~"feature::maintenance"
• ~"tooling::pipelines"
• ~"tooling::workflow"

Reference issues

https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/488