chore(dependabot): use Dependabot for pre-commit hook updates

See: https://github.blog/changelog/2026-03-10-dependabot-now-supports-pre-commit-hooks/

Author: tueda

.github/dependabot.yml

@@ -5,5 +5,8 @@ updates:
     directory: /
     schedule:
       interval: weekly
-    allow:
-      - dependency-type: direct
+
+  - package-ecosystem: pre-commit
+    directory: /
+    schedule:
+      interval: weekly