Update actions/checkout requirement to v2.3.4 (#720)

Author: dependabot[bot]

.github/workflows/sauce.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
       - name: Set up node
         uses: actions/setup-node@v2
         with: