docs(toh-6): Fix typo in 'Add/Delete in the HeroesComponent' section.

closes angular#1603

Author: jevonearth

public/docs/ts/latest/tutorial/toh-pt6.jade

@@ -289,7 +289,7 @@ figure.image-display
 +makeExample('toh-6/ts/app/heroes.component.ts', 'add', 'app/heroes.component.ts (add)')(format=".")
 :marked
   The `HeroDetailComponent` does most of the work. All we do is toggle an `*ngIf` flag that
-  swaps it into the DOM when were add a hero and remove it from the DOM when the user is done.
+  swaps it into the DOM when we add a hero and removes it from the DOM when the user is done.
 
   The *delete* logic is a bit trickier.
 +makeExample('toh-6/ts/app/heroes.component.ts', 'delete', 'app/heroes.component.ts (delete)')(format=".")