Detect mergequeue branch in another way

Building the image for the readonly branch is not needed as we already
know this should work in the PR, only if someone would force merging
before the CI passes we would need this.

Author: Michael Vasseur

.github/workflows/build-contributor-container-PR.yml

@@ -12,7 +12,7 @@ jobs:
   pr-contributor:
     if: ${{ !(github.repository == 'domjudge/domjudge-packaging' &&
               github.ref == 'refs/heads/main') &&
-            github.event.action != 'enqueued' &&
+            !contains(github.ref, 'gh-readonly-queue') &&
             (github.event_name == 'pull_request_target' ||
              github.event.pull_request.head.repo.full_name != github.repository) }}
     runs-on: ubuntu-latest

.github/workflows/build-domjudge-container-PR.yml

@@ -13,7 +13,7 @@ jobs:
   pr-domjudge:
     if: ${{ !(github.repository == 'domjudge/domjudge-packaging' &&
               github.ref == 'refs/heads/main') &&
-            github.event.action != 'enqueued' &&
+            !contains(github.ref, 'gh-readonly-queue') &&
             (github.event_name == 'pull_request_target' ||
              github.event.pull_request.head.repo.full_name != github.repository) }}
     runs-on: ubuntu-latest

.github/workflows/build-gitlab-container-PR.yml

@@ -10,7 +10,7 @@ jobs:
   pr-gitlab:
     if: ${{ !(github.repository == 'domjudge/domjudge-packaging' &&
               github.ref == 'refs/heads/main') &&
-            github.event.action != 'enqueued' &&
+            !contains(github.ref, 'gh-readonly-queue') &&
             (github.event_name == 'pull_request_target' ||
              github.event.pull_request.head.repo.full_name != github.repository) }}
     name: PR GitLab image