chore(ci): run CodeQL only on nightly schedule

Run CodeQL daily at 00:00 Asia/Tokyo and remove all other workflow triggers.

.github/workflows/codeql.yml

@@ -1,9 +1,8 @@
 name: CodeQL
 on:
-  pull_request:
   schedule:
-    - cron: '11 3 * * 1'
-  workflow_dispatch:
+    # Daily at 00:00 Asia/Tokyo (UTC+09:00).
+    - cron: '0 15 * * *'
 permissions:
   contents: read
 concurrency: