EOL cleanup

The old release reaches its end of life one month after the new release gets released. At that point a few cleanup tasks need to be done.

  1. Set the EOL channel status from deprecated to unmaintained in infra. Examples:

  2. Once this is merged, update the nixos-search repository to reflect that status on search.nixos.org.

    nix --extra-experimental-features "nix-command flakes" flake lock --update-input nixos-infra

  3. Close all pull requests that target one of the the old release- or staging-branches

  4. Prune old backport labels

Now create a PR that contains the following changes:

  1. Remove the old release from the periodic merge workflows

  2. Remove the references to the old release in .github/PULL_REQUEST_TEMPLATE.md

    Examples: 25.05

  3. Remove the references to the old release in .github/ISSUE_TEMPLATE/*

    Examples: 25.05

  4. Remove the old release branch from auto-labeler in .github/labeler-no-sync.yml

    Examples: 25.05

  5. Increase the oldestSupportedRelease in lib/trivial.nix to match the oldest supported release.

    Note: This may need a seperate PR as it can be breaking.

    Examples: 22.05

  6. Remove old release from LXC/Incus image server

    Ping Adam C. Stephens or open a Pull Request to lxc/lxc-ci

Last but not least, update the Nixpkgs branch protection rules and remove the old branch from the Merge Queue rule at: https://github.com/NixOS/org/blob/main/rulesets/nixpkgs/require-merge-queue.json