Remove old webgl enable button

demo/client.ts

@@ -118,7 +118,6 @@ if (document.location.pathname === '/test') {
 } else {
   createTerminal();
   document.getElementById('dispose').addEventListener('click', disposeRecreateButtonHandler);
-  document.getElementById('webgl').addEventListener('click', () => term.loadAddon(new WebglAddon()));
 }
 
 function createTerminal(): void {

demo/index.html

@@ -41,7 +41,6 @@
     <hr/>
     <p><strong>Attention:</strong> The demo is a barebones implementation and is designed for the development and evaluation of xterm.js only. Exposing the demo to the public as is would introduce security risks for the host.</p>
     <button id="dispose" title="This is used to testing memory leaks">Dispose terminal</button>
-    <button id="webgl">Enable WebGL Renderer</button>
     <script src="dist/client-bundle.js" defer ></script>
   </body>
 </html>