docs: update deprecated browserDynamicPlatform to platformBrowserDynamic

Author: MBing

public/docs/_examples/router/ts/app/main.ts

@@ -1,6 +1,6 @@
 // #docregion
-import { browserDynamicPlatform } from '@angular/platform-browser-dynamic';
+import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
 
 import { AppModule } from './app.module';
 
-browserDynamicPlatform().bootstrapModule(AppModule);
+platformBrowserDynamic().bootstrapModule(AppModule);