ci: bump snok/container-retention-policy from 1 to 2 (#4710)

Bumps [snok/container-retention-policy](https://github.com/snok/container-retention-policy) from 1 to 2.
- [Release notes](https://github.com/snok/container-retention-policy/releases)
- [Commits](https://github.com/snok/container-retention-policy/compare/v1...v2)

---
updated-dependencies:
- dependency-name: snok/container-retention-policy
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ghcr-retention.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Delete 'dev' containers older than a week
-        uses: snok/container-retention-policy@v1
+        uses: snok/container-retention-policy@v2
         with:
           image-names: dev-server,dev-ldap,dev-proxy
           cut-off: One week ago UTC