docs(tabs): use correct syntax

Author: thetaPC

static/usage/v8/tabs/router/angular/app_module_ts.md

@@ -11,7 +11,7 @@ import { ExampleComponent } from './example.component';
 import { AppRoutingModule } from './app-routing.module';
 
 @NgModule({
-  imports: [BrowserModule, FormsModule, AppRoutingModule, IonicModule.forRoot()],
+  imports: [BrowserModule, FormsModule, AppRoutingModule, IonicModule.forRoot({})],
   declarations: [AppComponent, ExampleComponent],
   bootstrap: [AppComponent],
 })