docs: simplify deleteHero method in tutorial (angular#41303)

Fixes angular#41233

PR Close angular#41303

Author: MariosRadis

aio/content/examples/toh-pt6/src/app/hero.service.ts

@@ -104,8 +104,7 @@ export class HeroService {
 
   // #docregion deleteHero
   /** DELETE: delete the hero from the server */
-  deleteHero(hero: Hero | number): Observable<Hero> {
-    const id = typeof hero === 'number' ? hero : hero.id;
+  deleteHero(id: number): Observable<Hero> {
     const url = `${this.heroesUrl}/${id}`;
 
     return this.http.delete<Hero>(url, this.httpOptions).pipe(

aio/content/examples/toh-pt6/src/app/heroes/heroes.component.ts

@@ -36,7 +36,7 @@ export class HeroesComponent implements OnInit {
   // #docregion delete
   delete(hero: Hero): void {
     this.heroes = this.heroes.filter(h => h !== hero);
-    this.heroService.deleteHero(hero).subscribe();
+    this.heroService.deleteHero(hero.id).subscribe();
   }
   // #enddocregion delete