Run yamllint job on gitlab-ci integrations

Otherwise no pipeline is created at all in these merge requests, which
prevents the MR from being merged.

manifest-integration.yml

@@ -37,9 +37,6 @@ workflow:
       when: never
     - if: $CI_MERGE_REQUEST_SOURCE_PROJECT_ID != $CI_MERGE_REQUEST_PROJECT_ID
       when: never
-    # Do not run pipeline for integrate/gitlab-ci/ integrations
-    - if: $CI_COMMIT_REF_NAME =~ /^integrate\/gitlab-ci\/.*/
-      when: never
     # FIXME: Unfortunately we cannot use variables in regular expressions due to a
     # GitLab limitation: https://gitlab.com/gitlab-org/gitlab/-/issues/209904
     # As soon as this get fixed, use the regex based rules below instead of checking
@@ -57,9 +54,14 @@ workflow:
 # --------------------------------------------------------------------------------------
 # Stage: infrastructure
 # --------------------------------------------------------------------------------------
+.skip-for-gitlab-ci-integrations:
+  rules:
+    - if: $CI_COMMIT_REF_NAME !~ /^integrate\/gitlab-ci\/.*/
+
 generate-pipelines:
   extends:
     - .infrastructure
+    - .skip-for-gitlab-ci-integrations
   script:
     # The job generation script implicitly passes the OS environment to the template, so
     # that the template has access to all GitLab CI variables. Hence there is no need
@@ -73,6 +75,8 @@ generate-pipelines:
       - manifest-integration-pipelines.yml
 
 trigger-pipelines:
+  extends:
+    - .skip-for-gitlab-ci-integrations
   stage: infrastructure
   needs:
     - generate-pipelines