Merge branch 'dj-runner-use-gitlab-registry' into 'master'

Use GitLab registry for default runner image

See merge request gitlab-org/gitlab!75675

qa/qa/resource/runner.rb

@@ -19,7 +19,7 @@ module QA
       end
 
       def image
-        @image || 'gitlab/gitlab-runner:alpine'
+        @image || 'registry.gitlab.com/gitlab-org/gitlab-runner:alpine'
       end
 
       def executor