docs: fix typo (#10019)

docs/content/1.docs/1.getting-started/5.routing.md

@@ -95,7 +95,7 @@ Example of an `auth` middleware protecting the `/dashboard` page:
 
 ```ts [middleware/auth.ts]
 export default defineNuxtRouteMiddleware((to, from) => {
-  // isAuthenticated() is an example method verifying if an user is authenticated
+  // isAuthenticated() is an example method verifying if a user is authenticated
   if (isAuthenticated() === false) {
     return navigateTo('/login')
   }