ci: skip forks when labeling prs

Signed-off-by: Michael Molisani <mmolisani@bloomberg.net>

Author: molisani

.github/workflows/pr_labels.yml

@@ -9,6 +9,8 @@ on:
 
 jobs:
     main:
+        # Only run on local PRs, not forks
+        if: github.event.pull_request.head.repo.full_name == github.repository
         runs-on: ubuntu-latest
         steps:
             - uses: actions/checkout@v4