Cancel in-progress scheduled GHA runs.

These were already being grouped because we group by branch name for scheduled workflow runs.  By not canceling in-progress runs, a single stalled execution could block our CI indefinitely.

PiperOrigin-RevId: 692298661

.github/workflows/test_runner.yml

@@ -48,7 +48,7 @@ permissions:
 
 concurrency:
   group: ${{ github.event_name }}-${{ github.workflow }}-${{ github.head_ref || github.ref }}
-  cancel-in-progress: ${{ contains(fromJSON('["pull_request", "pull_request_target", "workflow_dispatch"]'), github.event_name) }}
+  cancel-in-progress: ${{ contains(fromJSON('["pull_request", "pull_request_target", "workflow_dispatch", "schedule"]'), github.event_name) }}
 
 jobs:
   set-vars: