docs(router): get rid of unnecessary line in wildcard route example and fixing wildcard docregions (#37127)

The wildcard example leads to display a 404 page with the PageNotFoundComponent. But before, there is a wildcard to redirect to the FirstComponent and because of the routes order the FirstComponent will be displayed; which it is not the target of the wildcard route example code. Also, fixing some wildcard docregions
PR Close #37127

aio/content/examples/router/src/app/app-routing.module.8.ts

@@ -6,13 +6,11 @@ import { Routes, RouterModule } from '@angular/router'; // CLI imports router
 const routes: Routes = [
   { path: 'first-component', component: FirstComponent },
   { path: 'second-component', component: SecondComponent },
-  // #enddocregion routes
+  // #enddocregion routes, routes-with-wildcard
   { path: '',   redirectTo: '/first-component', pathMatch: 'full' }, // redirect to `first-component`
-  { path: '**', component: FirstComponent },
-  // #enddocregion redirect
+  // #docregion routes-with-wildcard
   { path: '**', component: PageNotFoundComponent },  // Wildcard route for a 404 page
   // #docregion routes
-  // #docregion redirect
 ];
 // #enddocregion routes, routes-with-wildcard, redirect