fix: Default to a relative path for the admin backend URL (#9947)

packages/core/framework/src/config/types.ts

@@ -72,7 +72,7 @@ export type AdminOptions = {
    */
   outDir?: string
   /**
-   * The URL of your Medusa application. This is useful to set when you deploy the Medusa application.
+   * The URL of your Medusa application. Defaults to the browser origin. This is useful to set when running the admin on a separate domain.
    *
    * @example
    * ```ts title="medusa-config.ts"