Add missing runner tags and triggers for ymllint

.gitlab-ci.yml

@@ -10,6 +10,12 @@ variables:
 yamllint:
   stage: lint
   image: registry.gitlab.com/pipeline-components/yamllint:latest
+  tags:
+    - 'docker'
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+    - if: '$CI_COMMIT_BRANCH && $CI_OPEN_MERGE_REQUESTS'
+      when: never
   script:
     - yamllint .