Link to React documentation for code splitting (#7686)

The official documentation offers a simpler way of achieving route based code splitting.

Author: Hugodby

docusaurus/docs/code-splitting.md

@@ -51,6 +51,6 @@ You can also use it with `async` / `await` syntax if you prefer it.
 
 ## With React Router
 
-If you are using React Router check out [this tutorial](https://serverless-stack.com/chapters/code-splitting-in-create-react-app.html) on how to use code splitting with it. You can find the companion GitHub repository [here](https://github.com/AnomalyInnovations/serverless-stack-demo-client/tree/code-splitting-in-create-react-app).
+If you are using React Router check out [this tutorial](https://reactjs.org/docs/code-splitting.html#route-based-code-splitting)
 
 Also check out the [Code Splitting](https://reactjs.org/docs/code-splitting.html) section in React documentation.