Mark v22.12 as EOL (2023-07-06)

A month after a new release has been published:

• make the postmarketos-release-upgrade-gtk3 package available in the old release, and let all postmarketos-ui- packages depend on it (see git log of previous EOL branch)
  • ensure it builds locally with pmbootstrap
  • push it to the branch
  • make sure bpo built and released the updated packages
• drop the old release from monitoring
• drop the "oldold -> old" release check from postmarketos-release-upgrade CI
• bpo: configure images so they don't get built for the old release anymore
• bpo: configure branches so we don't try to build packages for old branches anymore
  • e.g. on startup all branches are checked for new packages, we should keep the amount of branches that get checked minimal
• pmaports.git channels.cfg: change description:
  • "Old release (unsupported)"
• Update Releases, move the release from active to old
• Go through issues assigned to the old release
  • e.g. https://gitlab.postmarketos.org/postmarketos/pmaports/-/issues?label_name[]=release-v21.03
  • close or re-label them as it makes sense