ci: limit labeler to small pull requests

.github/workflows/labeler.yml

@@ -18,7 +18,17 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository_owner == 'nix-community'
     steps:
+      - name: Get changed files count
+        id: count
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          COUNT=$(gh pr diff $PR_NUMBER --name-only | grep '^modules/' | wc -l)
+          echo "count=$COUNT" >> "$GITHUB_OUTPUT"
+
       - uses: actions/labeler@v6
+        if: steps.count.outputs.count <= 10
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           sync-labels: true