ci: deduplicate running workflows (#1751)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.github/workflows/checks.yml

@@ -1,6 +1,10 @@
 name: checks
 on: [pull_request, workflow_dispatch]
 
+concurrency:
+  cancel-in-progress: true
+  group: ${{ github.workflow }}-${{ github.ref }}
+
 env:
   ACT_OWNER: ${{ github.repository_owner }}
   ACT_REPOSITORY: ${{ github.repository }}