adding parameter placeholder

Author: yucwan

articles/spring-cloud/spring-cloud-quickstart-launch-app-cli.md

@@ -54,7 +54,7 @@ az extension add --name spring-cloud
     ```azurecli
         az login
         az account list -o table
-        az account set --subscription
+        az account set --subscription <Name or ID of subscription from the last step>
     ```
 
 2. Prepare a name for your Azure Spring Cloud service.  The name must be between 4 and 32 characters long and can contain only lowercase letters, numbers, and hyphens.  The first character of the service name must be a letter and the last character must be either a letter or a number.