docs: update admin extension docs (#4778)

* docs: update admin extension docs

* eslint fixes

* fix broken links

* fix broken link

* added admin upgrade guide

* fix lint errors

www/docs/content/medusa-react/overview.mdx

@@ -213,16 +213,6 @@ Learn more about how you can use mutations in [Tanstack Query’s documentation]
 
 ### Custom Hooks
 
-:::note
-
-This feature is available in the `beta` version of Medusa React, which also requires the `beta` version of the Medusa core. You can install them with the following command:
-
-```bash
-npm install medusa-react@beta @medusajs/medusa@beta
-```
-
-:::
-
 Medusa React provides three utility hooks that allows developers to consume their admin custom endpoints using the same Medusa React methods and conventions.
 
 #### useAdminCustomQuery