Avoid to label Starter in general due to EoA

Avoid to label Starter due to its EoA, except for issues for maintenance of existing features in Starter/Bronze: https://docs.gitlab.com/ee/subscriptions/bronze_starter.html

Action items

• (If applicable) Add documentation to the handbook pages for Triage Operations => gitlab-com/www-gitlab-com!81683 (merged)
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Week-in-review
• gitlab-org/gitlab!61331 (merged)