docs(toh-3): corrected incorrect displayed file name in tutorial (#3457)

Author: xadhix

public/docs/ts/latest/tutorial/toh-pt3.jade

@@ -177,7 +177,7 @@ a#add-hero-detail
   Coordinate the master `AppComponent` with the `HeroDetailComponent`
   by binding the `selectedHero` property of the `AppComponent`
   to the `hero` property of the `HeroDetailComponent`.
-+makeExample('toh-3/ts/app/app.component.1.html', 'hero-detail-binding', 'app.component.html (excerpt)')(format='.')
++makeExample('toh-3/ts/app/app.component.1.html', 'hero-detail-binding', 'app.component.ts (excerpt)')(format='.')
 :marked
  Now every time the `selectedHero` changes, the `HeroDetailComponent` gets a new hero to display.