chore: upgrade local dev node version (#481)

Author: chdeskur

fern/products/docs/pages/getting-started/preview-changes-locally.mdx

@@ -10,7 +10,7 @@ Fern offers two ways to preview changes to your documentation: a [local developm
 
 Fern enables you to view changes to your documentation in a locally hosted environment.
 
-<Info>**Prerequisite**: Please install Node.js (version 18) before proceeding.</Info>
+<Info>**Prerequisite**: Please install Node.js (version 18+) before proceeding.</Info>
 
 Follow these steps to install and run the Fern CLI: