Update Docker checkout action to v2 🐳

Author: artkirienko

.github/workflows/docker-image.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
       - name: Build the Docker image
         run: docker build . --file Dockerfile --tag bakery:$(date +%s)
       - name: Hadolint Action