remove subtitle control

docs/mobile.html

@@ -101,8 +101,8 @@
                 {
                     width: 200,
                     html: '切换字幕',
-                    tooltip: '中日双语',
-                    icon: '<img width="22" heigth="22" src="/assets/img/indicator.svg">',
+                    tooltip: '双语',
+                    icon: '<img width="22" heigth="22" src="/assets/img/subtitle.svg">',
                     selector: [
                         {
                             html: '显示字幕',
@@ -116,7 +116,7 @@
                         },
                         {
                             default: true,
-                            html: '中日双语',
+                            html: '双语',
                             url: '/assets/sample/subtitle.srt'
                         },
                         {