Add permission to write to issues

See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions

.github/workflows/benchmarks.yml

@@ -14,6 +14,8 @@ jobs:
       github.event_name == 'pull_request' || 
       (github.event_name == 'issue_comment' && contains(github.event.comment.body, '/rerun-benchmarks'))
     runs-on: ubuntu-latest
+    permissions:
+      issues: write
     steps:
       - name: Checkout PR branch
         uses: actions/checkout@v4