Handle the fact Metadata Cleaner is unmaintained

https://gitlab.com/rmnvgr/metadata-cleaner#unmaintained

After more than 3 years, I unfortunately don't have time to maintain Metadata Cleaner anymore. If someone wants to continue working on it, please feel free to fork the repository.

Thanks to everyone who contributed over the years.

To Do

• Ensure the Debian maintainers are aware that upstream gave up maintenance, so they can make an informed decision in time for Trixie.
• Encourage folks to take over maintenance
  • Mention the problem on mat-dev@
  • Draft call for help
  • Get call for help reviewed/co-signed by relevant stakeholders
    • jvoisin
    • sajolida
  • Send call for help
    • tails-dev@
    • tor-dev@
    • Tor forum
      • https://forum.torproject.org/t/metadata-cleaner-is-looking-for-a-new-co-maintainer/17021
• If this fails, consider broadening the net
  • Tails newsletter
  • Tor newsletter
    • No, this does not fit.
  • Tails social media
  • Tor social media
  • any other relevant venue?
• If the above fails, consider becoming upstream ourselves, like we're upstream for Onion Circuits. This will require a decision wrt. whether the cost/benefit is worth it.

Original report

Title = "Remove Metadata Cleaner (unmaintained)"

EDIT: Unfortunately it was a good software, but keeping an unmaintained app in Tails is a security risk, if some security vulnerability was found later in the app.