[docs] Fix 404 link to Next.js

Reported in https://app.ahrefs.com/site-audit/3524616/data-explorer?columns=pageRating%2Curl%2Ctraffic%2ChttpCode%2CcontentType%2Cdepth%2CincomingAllLinks&current=11-10-2024T023122&filterId=9b88587038fc9bb2e08e0ff143d5f328&issueId=c64d89a6-d0f4-11e7-8ed1-001e67ed4656&sorting=-pageRating

Author: oliviertassinari

docs/data/joy/customization/dark-mode/dark-mode.md

@@ -115,7 +115,7 @@ export default class MyDocument extends Document {
 
 ### Next.js App Router
 
-To use the Joy UI API with a Next.js project with the App Router, add the following code to the [root layout](https://nextjs.org/docs/app/building-your-application/routing/layouts-and-templates#root-layout-required) file in order to prevent flickering:
+To use the Joy UI API with a Next.js project with the App Router, add the following code to the [root layout](https://nextjs.org/docs/app/building-your-application/routing/pages-and-layouts#root-layout-required) file in order to prevent flickering:
 
 ```jsx title="app/layout.js"
 import InitColorSchemeScript from '@mui/joy/InitColorSchemeScript';

docs/data/material/customization/css-theme-variables/configuration.md

@@ -176,7 +176,7 @@ createTheme({
 
 ### Next.js App Router
 
-Add the following code to the [root layout](https://nextjs.org/docs/app/building-your-application/routing/layouts-and-templates#root-layout-required) file:
+Add the following code to the [root layout](https://nextjs.org/docs/app/building-your-application/routing/pages-and-layouts#root-layout-required) file:
 
 ```jsx title="app/layout.js"
 import InitColorSchemeScript from '@mui/material/InitColorSchemeScript';