ci: revert to Ubuntu Focal for Docker builds

due to yet another more recent bug, this time at the runner host side, it seems: actions/runner-images#9848 (comment)

Signed-off-by: MichaIng <micha@dietpi.com>

Author: MichaIng

.github/workflows/docker.yml

@@ -12,7 +12,8 @@ permissions:
 jobs:
   docker:
     if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.owner.login != github.event.pull_request.base.repo.owner.login
-    runs-on: ubuntu-24.04
+    # ToDo: Switch to Ubuntu Noble once runner host end cancellations are fixed: https://github.com/actions/runner-images/issues/9848#issuecomment-2137140734
+    runs-on: ubuntu-22.04
 
     permissions:
       packages: write