docs: align toh-pt5 code with toh-pt4 (angular#41234)

This commit aligns the code of `HeroService` `getHeroes()` and
`getHero()` methods in `toh-pt5` with that of `toh-pt4`. I.e. it applies
the changes from angular#40419 to `toh-pt5`.

PR Close angular#41234

Author: gkalpak

aio/content/examples/toh-pt5/src/app/hero.service.ts

@@ -12,16 +12,16 @@ export class HeroService {
   constructor(private messageService: MessageService) { }
 
   getHeroes(): Observable<Hero[]> {
-    // TODO: send the message _after_ fetching the heroes
+    const heroes = of(HEROES);
     this.messageService.add('HeroService: fetched heroes');
-    return of(HEROES);
+    return heroes;
   }
 
   // #docregion getHero
   getHero(id: number): Observable<Hero> {
-    // TODO: send the message _after_ fetching the hero
+    const hero = HEROES.find(h => h.id === id);
     this.messageService.add(`HeroService: fetched hero id=${id}`);
-    return of(HEROES.find(hero => hero.id === id));
+    return of(hero);
   }
   // #enddocregion getHero
 }