ci(issue-labeler): `pull_request` -> `pull_request_target`

.github/workflows/issue-labeler.yml

@@ -3,7 +3,7 @@ name: Issue Labeler
 on:
   issues:
     types: [opened]
-  pull_request:
+  pull_request_target:
     types: [opened]
   workflow_dispatch:
     inputs: