Restrict action to internal PRs (#13936)

Author: subhramit

.github/workflows/on-pr-opened-updated.yml

@@ -161,12 +161,16 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
   remove_label:
-    if: github.repository == 'JabRef/jabref'
+    if: >
+      (github.repository == 'JabRef/jabref') &&
+      (github.event.pull_request.head.repo.full_name == 'JabRef/jabref')
     name: 'Remove label "status: changes-required"'
     runs-on: ubuntu-latest
     steps:
       - run: |
           gh issue --repo ${{ github.repository }} edit ${{ github.event.pull_request.number }} --remove-label "status: changes-required"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
   upload-pr-number:
     if: github.repository == 'JabRef/jabref'
     runs-on: ubuntu-latest