ci: ensure unique group ID to prevent workflows from getting cancelled (#31806)

ci: ensure unique group ID to prevent workflows from cancelling
diff --git a/.github/workflows/server-tests-mariadb.yml b/.github/workflows/server-tests-mariadb.yml
index 64134bc..e3b92fd 100644
--- a/.github/workflows/server-tests-mariadb.yml
+++ b/.github/workflows/server-tests-mariadb.yml
@@ -27,7 +27,7 @@
         type: string
 
 concurrency:
-  group: server-mariadb-develop-${{ github.event.number }}
+  group: server-mariadb-develop-${{ github.event_name }}-${{ github.event.number || github.event_name == 'workflow_dispatch' && github.run_id || '' }}
   cancel-in-progress: true
 
 jobs: