Update discord invite link

Update discord invite link

web/app/header.tsx

 import Link from "next/link"
 
 const navigation = [
-  { name: 'Discord', href: 'https://discord.gg/MrfB5FbNWN' },
+  { name: 'Discord', href: 'https://discord.com/invite/ollama' },
   { name: 'GitHub', href: 'https://github.com/jmorganca/ollama' },
   { name: 'Download', href: '/download' },
 ]
@@ -23,4 +23,4 @@ export default function Header() {
       </nav>
     </header>
   )
-}
+}
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