ci: add release-please concurrency settings

Author: suchapalaver

.github/workflows/containers.yml

@@ -13,6 +13,10 @@ env:
 
 jobs:
   release-please:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    concurrency:
+      group: release-please-${{ github.ref }}
+      cancel-in-progress: true
     permissions:
       contents: write
       pull-requests: write