update mobile demo

docs/assets/css/mobile.css

@@ -10,6 +10,7 @@ html, body {
 
 .artplayer-app {
     width: 100%;
+    height: 50%;
 }
 
 .tip {

docs/assets/js/mobile.js

@@ -58,10 +58,6 @@ var art = new Artplayer({
     whitelist: ['*'],
 });
 
-art.on('ready', function () {
-    art.autoHeight = true;
-});
-
 Artplayer.config.events.forEach(function (item) {
     art.on('video:' + item, function (event) {
         console.log('video: ' + event.type);