added missing callout CSS class

docs/getting-started/devenv/get-started-with-wp-env.md

@@ -44,7 +44,7 @@ wp-env start
 
 Once the script completes, you can access the local environment at: `http://localhost:8888`. Log into the WordPress dashboard using username `admin` and password `password`.
 
-<div class="callout-tip">
+<div class="callout callout-tip">
     Some projects, like Gutenberg, include their own specific <code>wp-env</code> configurations, and the documentation might prompt you to run <code>npm run start wp-env</code> instead.
 </div>