CI: Also cancel stale Bandit runs

Author: callumfare

.github/workflows/bandit.yml

@@ -3,6 +3,10 @@ name: Bandit
 
 on: [push, pull_request, workflow_dispatch]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   linux:
     name: Bandit