Cancel duplicate CI workflow

Author: pllim

.github/workflows/ci_workflows.yml

@@ -10,6 +10,10 @@ on:
     # Monthly cron
     - cron: '0 8 1 * *'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   tests:
     runs-on: ${{ matrix.os }}