Remove the specific AppUserModelID

It's not necessary for Notification on the latest Electron.

src/main.js

@@ -49,9 +49,6 @@ var mainWindow = null;
 var trayIcon = null;
 var willAppQuit = false;
 
-// For toast notification on windows
-app.setAppUserModelId('yuya-oc.electron-mattermost');
-
 // Quit when all windows are closed.
 app.on('window-all-closed', function() {
   // On OS X it is common for applications and their menu bar