update: add x-ai/grok-4 to grok-x-ai.mdx

Author: Mortza81

src/pages/ai/grok-x-ai.mdx

@@ -44,7 +44,7 @@ import Head from "next/head";
   {[
     {text: <Important>x-ai/grok-3-mini-beta</Important>,},
     {text: <Important>x-ai/grok-3-beta</Important>,},
-
+    {text: <Important>x-ai/grok-4</Important>,},
   ].map((item, index) => (
     <li
       key={index}
@@ -569,4 +569,4 @@ print(response)
   ]}
 />
 
-</Layout>
+</Layout>