Update build-check-tutorial-site.yml

Author: hb326

.github/workflows/build-check-tutorial-site.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: "ubuntu-latest"
     steps:
     - uses: actions/checkout@v2
     - name: Setup Ruby