PLT-4343 Fixes for mobile main menu (#4148)

* Fixed mobile app link in the main menu to be displayed on mobile browsers

* Fixed doubled up dividers in mobile menu

* Added scrolling to mobile main menu

webapp/utils/async_client.jsx

@@ -911,7 +911,7 @@ export function getSuggestedCommands(command, suggestionId, component) {
         (data) => {
             var matches = [];
             data.forEach((cmd) => {
-                if (cmd.trigger !== 'shortcuts' || !UserAgent.isMobileApp()) {
+                if (cmd.trigger !== 'shortcuts' || !UserAgent.isMobile()) {
                     if (('/' + cmd.trigger).indexOf(command) === 0) {
                         const s = '/' + cmd.trigger;
                         let hint = '';