change URL to match desired local build page (#1216)

Author: nklincoln

packages/composer-playground/src/app/app.component.html

@@ -15,7 +15,7 @@
  </button>
  </li>
  <li *ngIf="!usingLocally">
- <a href="https://hyperledger.github.io/composer/getting-started/using-playground-locally.html" target="_blank">
+ <a href="https://hyperledger.github.io/composer/installing/using-playground-locally.html" target="_blank">
  <svg class="nav-icon" aria-hidden="true">
  <use xlink:href="#icon-simple_docker"></use>
  </svg>