Switch unsafe-reviewers.yml to use pull_request_target

.github/workflows/unsafe-reviewers.yml

@@ -1,7 +1,7 @@
 name: Unsafe Reviewers Check
 on:
   workflow_dispatch:
-  pull_request:
+  pull_request_target:
     types: [opened, reopened, synchronize]
 
 # https://docs.github.com/en/actions/using-jobs/assigning-permissions-to-jobs