docs: fix Node.js version text in installation page (#14015)

* Fix Node.js version text in installation page

Node.js version 20 is more stabler than v20+.
Issue found in Node.js version v25.1.0
https://github.com/medusajs/medusa/issues/14011

* Update www/apps/book/app/learn/installation/page.mdx

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

---------

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

www/apps/book/app/learn/installation/page.mdx

@@ -28,7 +28,7 @@ While this is the recommended way to create a Medusa application, you can altern
 
 <Prerequisites items={[
   {
-    text: "Node.js v20+",
+    text: "Node.js v20+ (LTS versions)",
     link: "https://nodejs.org/en/download"
   },
   {