message: docs(aio): change `HeroService` to `MessagesComponent`
  Someone probably forgot to change this when coping the sentence from a previous section.
  PR Close
diff: @@ -348,7 +348,7 @@ Open `MessagesComponent` and import the `MessageService`.
  Modify the constructor with a parameter that declares a **public** `messageService` property.
  Angular will inject the singleton `MessageService` into that property
  -when it creates the `HeroService`.
  +when it creates the `MessagesComponent`.
  <code-example
  path="toh-pt4/src/app/messages/messages.component.ts" region="ctor">
  