Avoid duplicate pipeline due to container scanning job

Regression introduced by https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61850

lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml

@@ -40,4 +40,5 @@ container_scanning:
   rules:
     - if: $CONTAINER_SCANNING_DISABLED
       when: never
-    - if: $GITLAB_FEATURES =~ /\bcontainer_scanning\b/
+    - if: $CI_COMMIT_BRANCH &&
+          $GITLAB_FEATURES =~ /\bcontainer_scanning\b/