Hide Alt+[0-9] checkbox on mobile

Mobile users don't typically have an Alt key

index.html

@@ -484,12 +484,12 @@ npm run build-electron-{windows, darwin, linux}</pre>
                   </div>
                 </form>
               </li>
-               <li>
+              <li class="desktop">
                 <form class="form-inline" role="form">
                   <div class="checkbox">
                     <label>
                       <input type="checkbox" ng-model="settings.enableAltSwitcher">
-                      Use Alt+&lt;num&gt; to switch buffers
+                      Use Alt+[0-9] to switch buffers
                     </label>
                   </div>
                 </form>