fix strings

.github/workflows/backend.yml

@@ -29,7 +29,7 @@ jobs:
         password: ${{ secrets.DOCKER_PASSWORD }}
     - name: Build and Push template image
       uses: docker/build-push-action@v2 # https://github.com/docker/build-push-action
-        context: .
+        context: './backend'
         repository: parity/substrate-telemetry-backend
         push: ${{ startsWith(github.ref, 'refs/tags/') }}
         tags: latest

.github/workflows/frontend.yml

@@ -44,7 +44,7 @@ jobs:
     - name: Build and Push template image
       uses: docker/build-push-action@v2 # https://github.com/docker/build-push-action
       if: matrix.node-version == '12.x'
-        context: ./frontend/
+        context: './frontend'
         repository: parity/substrate-telemetry-frontend
         push: ${{ startsWith(github.ref, 'refs/tags/') }}
         tags: latest