Remove pitfall and update Next link (#6318)

* Remove pitfall and update Next link

* Fix other beta link

---------

Co-authored-by: Luna Wei <luwe@fb.com>

Author: lunaleaps

src/content/learn/start-a-new-react-project.md

@@ -89,14 +89,9 @@ These features are getting closer to being production-ready every day, and we've
 
 ### Next.js (App Router) {/*nextjs-app-router*/}
 
-**[Next.js's App Router](https://beta.nextjs.org/docs/getting-started) is a redesign of the Next.js APIs aiming to fulfill the React team’s full-stack architecture vision.** It lets you fetch data in asynchronous components that run on the server or even during the build.
+**[Next.js's App Router](https://nextjs.org/docs) is a redesign of the Next.js APIs aiming to fulfill the React team’s full-stack architecture vision.** It lets you fetch data in asynchronous components that run on the server or even during the build.
 
-Next.js is maintained by [Vercel](https://vercel.com/). You can [deploy a Next.js app](https://nextjs.org/docs/deployment) to any Node.js or serverless hosting, or to your own server. Next.js also supports [static export](https://beta.nextjs.org/docs/configuring/static-export) which doesn't require a server.
-<Pitfall>
-
-Next.js's App Router is **currently in beta and is not yet recommended for production** (as of Mar 2023). To experiment with it in an existing Next.js project, [follow this incremental migration guide](https://beta.nextjs.org/docs/upgrade-guide#migrating-from-pages-to-app).
-
-</Pitfall>
+Next.js is maintained by [Vercel](https://vercel.com/). You can [deploy a Next.js app](https://nextjs.org/docs/deployment) to any Node.js or serverless hosting, or to your own server. Next.js also supports [static export](https://nextjs.org/docs/app/building-your-application/deploying/static-exports) which doesn't require a server.
 
 <DeepDive>