chore: 贡献者更新工作流改为每周定时触发

移除 push 触发，仅保留每周一 schedule 触发。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: claude-code-best

.github/workflows/update-contributors.yml

@@ -1,11 +1,8 @@
 name: Update Contributors
 
 on:
-  push:
-    branches:
-      - main
   schedule:
-    - cron: '0 0 * * *'  # 每天更新一次
+    - cron: '0 0 * * 1'  # 每周一更新一次
 
 permissions:
   contents: write