CI: Avoid running on 'push' in mirrors / forks (#110063)

* CI: Avoid running on 'push' in mirrors / forks

* use single quotes

.github/workflows/pr-frontend-unit-tests.yml

@@ -10,6 +10,8 @@ permissions: {}
 
 jobs:
   detect-changes:
+    # Run on `grafana/grafana` main branch, or on pull requests to prevent double-running on mirrors
+    if: (github.event_name == 'pull_request' || (github.event_name == 'push' && github.repository == 'grafana/grafana'))
     name: Detect whether code changed
     runs-on: ubuntu-x64-small
     permissions:
@@ -166,4 +168,4 @@ jobs:
         with:
           needs: ${{ toJson(needs) }}
           failure-message: "One or more unit test jobs have failed"
-          success-message: "All unit tests completed successfully"
+          success-message: "All unit tests completed successfully"