Add .default-only to webpack-dev-server

webpack-dev-server is triggered on branch push
Fixes https://gitlab.com/gitlab-org/gitlab/issues/32160

.gitlab/ci/frontend.gitlab-ci.yml

@@ -230,6 +230,7 @@ webpack-dev-server:
     - .default-tags
     - .default-retry
     - .default-cache
+    - .default-only
     - .only-code-changes
   dependencies: ["setup-test-env", "compile-assets", "compile-assets pull-cache"]
   variables: