fix the alignment problem (#940)

serving/samples/source-to-url-go/README.md

@@ -78,17 +78,16 @@ available, but these are the key steps:
 1. Create a new `Service Account` manifest which is used to link the build
    process to the secret. Save this file as `service-account.yaml`:
    
-```yaml
-apiVersion: v1
-kind: ServiceAccount
-metadata:
+   ```yaml
+   apiVersion: v1
+   kind: ServiceAccount
+   metadata:
      name: build-bot
-secrets:
+   secrets:
      - name: basic-user-pass
-```
+   ```
 
-1. After you have created the manifest files, apply them to your cluster with
-   `kubectl`:
+1. After you have created the manifest files, apply them to your cluster with `kubectl`:
 
    ```shell
    $ kubectl apply --filename docker-secret.yaml