ci: concurrency control for postgres

.github/workflows/server-postgres-tests.yml

@@ -4,6 +4,10 @@ on:
   pull_request:
   workflow_dispatch:
 
+concurrency:
+  group: server-postgres-develop-${{ github.event.number }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ubuntu-18.04