Upgrade workflows to actions/checkout@v3

Author: bdunne

.github/workflows/ci.yaml

@@ -15,7 +15,7 @@ jobs:
         node-version:
         - 14
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Set up system
       run: bin/before_install
     - name: Set up Node