message: docs(aio): correct abbreviation
  change abbreviation from 'ES' to 'ES2015'. the 'ES2015' abbreviation is used elsewhere in the tutorial.
diff: @@ -918,7 +918,7 @@ such as `RouterLink` and `RouterOutlet`.
  ### Update *AppModule*
  Delete the routing configuration from `AppModule` and import the `AppRoutingModule`.
  -Use an ES `import` statement *and* add it to the `NgModule.imports` list.
  +Use an ES2015 `import` statement *and* add it to the `NgModule.imports` list.
  Here is the revised `AppModule`, compared to its pre-refactor state:
  