remove cron to prevent CI from being disabled

Author: mansona

.github/workflows/ci.yml

@@ -3,13 +3,13 @@ name: CI
 on:
   push:
     branches:
+      - main
       - master
-      - 'v*' # older version branches
-    tags:
-      - '*'
-  pull_request:
-  schedule:
-    - cron:  '0 3 * * *' # daily at 3am
+  pull_request: {}
+
+concurrency:
+  group: ci-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
 
 jobs:
   test: