Update actions/checkout action to v2

Author: renovate-bot

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
       - name: Set up docker buildx
         id: buildx
         uses: crazy-max/ghaction-docker-buildx@v1