refactor(docs-infra): update universal example to match latest CLI (#36483)

Update the `universal` example (and related files) to match what would
be generated by the latest CLI.

Fixes #35289

PR Close #36483

aio/content/examples/universal/src/app/app.server.module.ts

@@ -1,6 +1,5 @@
 import { NgModule } from '@angular/core';
 import { ServerModule } from '@angular/platform-server';
-import { ModuleMapLoaderModule } from '@nguniversal/module-map-ngfactory-loader';
 
 import { AppModule } from './app.module';
 import { AppComponent } from './app.component';
@@ -9,11 +8,10 @@ import { AppComponent } from './app.component';
   imports: [
     AppModule,
     ServerModule,
-    ModuleMapLoaderModule
   ],
   providers: [
     // Add universal-only providers here
   ],
-  bootstrap: [ AppComponent ],
+  bootstrap: [AppComponent],
 })
 export class AppServerModule {}

aio/content/examples/universal/src/main.ts

@@ -8,5 +8,7 @@ if (environment.production) {
   enableProdMode();
 }
 
-platformBrowserDynamic().bootstrapModule(AppModule)
-  .catch(err => console.error(err));
+document.addEventListener('DOMContentLoaded', () => {
+  platformBrowserDynamic().bootstrapModule(AppModule)
+    .catch(err => console.error(err));
+});