ci: cherry-pick to main by default

.github/workflows/cherry-pick-to-main.yml

@@ -5,7 +5,7 @@ on:
     # Run every 5 minutes
     - cron: '*/5 * * * *'
   workflow_dispatch:
-  pull_request:
+  pull_request_target:
     types: [opened, reopened]
     branches:
       - canary
@@ -23,7 +23,6 @@ jobs:
       - name: Add merge-to-main label
         uses: actions/github-script@v7
         with:
-          github-token: ${{ secrets.PAT_TOKEN }}
           script: |
             await github.rest.issues.addLabels({
               owner: context.repo.owner,