message: docs: fix http example to use correct property
  Fixes
  PR Close
diff: <h1>HTTP Sample</h1>
  <div>
  - <input type="checkbox" id="heroes" [checked]="toggleHeroes" (click)="toggleHeroes()">
  + <input type="checkbox" id="heroes" [checked]="showHeroes" (click)="toggleHeroes()">
  <label for="heroes">Heroes</label>
  <input type="checkbox" id="config" [checked]="showConfig" (click)="toggleConfig()">
  