Try to fix PR labeler

Reference: https://github.com/actions/labeler?tab=readme-ov-file#permissions

.github/workflows/pr-labeler.yml

@@ -1,5 +1,5 @@
 name: "PR size labeler"
-on: [pull_request]
+on: [pull_request_target]
 permissions:
   contents: read
   pull-requests: write