Fix typo in Next.js workers guide (#21557)

Author: mazn4

src/content/docs/workers/frameworks/framework-guides/nextjs.mdx

@@ -107,7 +107,7 @@ You can convert an existing Next.js application to run on Cloudflare
         			compatibility_date = "2025-03-25"
         			compatibility_flags = ["nodejs_compat"]
         			[assets]
-        			directory = "./dist"
+        			directory = ".open-next/assets"
         			binding = "ASSETS"
         		```
         	</WranglerConfig>