add enterprise plan callout

Author: devalog

fern/products/docs/pages/enterprise/self-hosted.mdx

@@ -3,6 +3,8 @@ title: Self-Hosted Documentation
 description: Fern supports self-hosting so that you can run your docs site on your own infrastructure.
 ---
 
+<Note>Self-hosted documentation is only available for the enterprise plan.</Note>
+
 Fern documentation websites are hosted on Fern's infrastructure by default. Self-hosting allows you to deploy your documentation site on your own infrastructure to meet specific security or compliance requirements.
 
 ## When to Use Self-Hosting