File Fedora Change Proposal for automated onboarding opt-out

[lbarcziova]

Followup of https://fedoraproject.org/wiki/Changes/AutomatedPackitOnboarding, where the decision was:

AGREED: The proposal is approved with the modification that it's just opt-in for F42. Switching to opt-out can be proposed for F43 (+9, 0, 0)
INFO: FESCo also requests that the Packit team investigate conditionalizing for known problematic packages such as rust-* to be excluded from future opt-out.

In this proposal, we should just propose this mechanism to be opt-out instead of opt-in decided in the previous change.

TODO:

• [ ] draft a text for proposal following https://docs.fedoraproject.org/en-US/program_management/changes_guide
  • include results from #2696
• [ ] get review by the team
• [ ] submit it following the guide

~~Change Checkpoint: Proposal submission deadline (System Wide Changes) Tue 2025-07-01~~ Let's aim for F45 (date TBA).