ci: limit acceptance test concurrency

Signed-off-by: Richard Steinmetz <richard@steinmetz.cloud>

.github/workflows/test.yml

@@ -56,7 +56,8 @@ jobs:
 
   acceptance-tests:
     concurrency:
-      group: acceptance-tests
+      group: acceptance-tests-${{ github.head_ref || github.run_id }}
+      cancel-in-progress: true
     runs-on: ubuntu-latest
 
     strategy: