update docker actions to v2

.github/workflows/backend.yml

@@ -22,14 +22,15 @@ jobs:
     - name: Build release and call executable
       working-directory: ./backend
       run: cargo run --release -- --help
-    - name: Build and Push template image
-      uses: docker/build-push-action@v1 # https://github.com/docker/build-push-action
+    - name: Login to Dockerhub
+      uses: docker/login-action@v1
       with:
         username: ${{ secrets.DOCKER_USERNAME }}
         password: ${{ secrets.DOCKER_PASSWORD }}
-        path: ./backend/
-        dockerfile: ./backend/Dockerfile
+    - name: Build and Push template image
+      uses: docker/build-push-action@v2 # https://github.com/docker/build-push-action
+        context: .
         repository: parity/substrate-telemetry-backend
         push: ${{ startsWith(github.ref, 'refs/tags/') }}
         tags: latest
-        add_git_labels: true
+        # add_git_labels: true