Update sanity-check.yml to use ubuntu-latest

Author: vvscode

.github/workflows/sanity-check.yml

@@ -4,7 +4,7 @@ on: pull_request
 
 jobs:
   lint:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v2