fix(js): correct npm command syntax to resolve EUPDATEARGS error (#8056)

Author: enes-sahin

src/pages/[platform]/start/manual-installation/index.mdx

@@ -150,7 +150,7 @@ defineBackend({
 You can also update an existing frontend app. To upgrade existing Amplify code-first DX (Gen 2) apps, use your Node.js package manager (for example, `npm`) to update relevant backend packages:
 
 ```bash title="Terminal" showLineNumbers={false}
-npm update @aws-amplify/backend@latest @aws-amplify/backend-cli@latest
+npm update @aws-amplify/backend @aws-amplify/backend-cli
 ```
 
 ## Next steps