fix typo

.github/workflows/gh-build-docs.yml

@@ -10,7 +10,7 @@ jobs:
     name: Build docs
     # The build stage could fail but we want the CI to keep moving.
     if: ${{ github.repository_owner == 'nvidia' && always() }}
-    runs-on: ubuntu-latest
+    runs-on: "ubuntu-latest"
     defaults:
       run:
         shell: bash -el {0}