docs: update example to use `nuxtApp.runWithContext` (#28000)

docs/2.guide/4.recipes/3.custom-usefetch.md

@@ -24,7 +24,7 @@ Let's pretend here that:
 - If the API responds with a `401` status code, we redirect the user to the `/login` page
 
 ```ts [plugins/api.ts]
-export default defineNuxtPlugin(() => {
+export default defineNuxtPlugin((nuxtApp) => {
   const { session } = useUserSession()
 
   const api = $fetch.create({
@@ -43,7 +43,7 @@ export default defineNuxtPlugin(() => {
     },
     async onResponseError({ response }) {
       if (response.status === 401) {
-        await navigateTo('/login')
+        await nuxtApp.runWithContext(() => navigateTo('/login'))
       }
     }
   })