[GitHub Actions] Update main branch sync schedule

Update "each hour" instead of "each 10 minutes".

Author: bader

.github/workflows/sync-main.yml

@@ -2,7 +2,7 @@ name: automatic sync main branch from llvm-project to llvm
 
 on:
   schedule:
-  - cron: '*/10 * * * *'
+  - cron: '0 */1 * * *'
 jobs:
   sync:
     runs-on: ubuntu-latest