Pin multi-labeler github action to stable version

Author: sparr

.github/workflows/summary-labeler.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: fuxingloh/multi-labeler@main
+      - uses: fuxingloh/multi-labeler@v4.0.0
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           config-path: '.github/summary-labels.yml'