docs(chore): make styles consistent for API doc headings

Closes #4816

modules/angular2/src/http/static_response.ts

@@ -12,7 +12,7 @@ import {isJsObject} from './http_utils';
  * usually instantiated by end-users, it is the primary object interacted with when it comes time to
  * add data to a view.
  *
- * #Example
+ * ### Example
  *
  * ```
  * http.request('my-friends.txt').subscribe(response => this.friends = response.text());