Add "pull-requests: write" permission to the labeler

Copied from the example at https://github.com/actions/labeler?tab=readme-ov-file#outputs
Trying to fix https://github.com/apache/avro/actions/runs/10460767435/job/28981928566?pr=3102
```
Run actions/labeler@v5
  with:
    repo-token: ***
    sync-labels: true
    configuration-path: .github/labeler.yml
    dot: true
The configuration file (path: .github/labeler.yml) was not found locally, fetching via the api
Warning: The action requires write permission to add labels to pull requests. For more information please refer to the action documentation: https://github.com/actions/labeler#permissions
Error: Resource not accessible by integration
```

Signed-off-by: Martin Tzvetanov Grigorov <[email protected]>

Author: martin-g

.github/workflows/labeler.yml

@@ -21,6 +21,9 @@ on: pull_request_target
 
 jobs:
   triage:
+    permissions:
+      contents: read
+      pull-requests: write
     runs-on: ubuntu-latest
     steps:
     - uses: actions/labeler@v5