Update status-checker action mode to warning

Author: gewarren

.github/workflows/check-for-build-warnings.yml

@@ -23,5 +23,4 @@ jobs:
     - uses: dotnet/docs-tools/actions/status-checker@main
       with:
         repo_token: ${{ secrets.GITHUB_TOKEN }}
-        docs_path: "docs"
-        url_base_path: "dotnet"
+        mode: "warning"