Use default branch settings in mono-repo.yaml (#4433)

Author: isoos

.github/workflows/dart.yml

@@ -2,6 +2,9 @@
 name: Dart CI
 on:
   push:
+    branches:
+      - main
+      - master
   pull_request:
   schedule:
     - cron: "0 0 * * 0"

mono_repo.yaml

@@ -3,11 +3,7 @@ self_validate: smoke_test
 pub_action: get
 
 github:
-  on:
-    push:
-    pull_request:
-    schedule:
-      - cron: "0 0 * * 0"
+  cron: "0 0 * * 0"
 
 merge_stages:
   - smoke_test