PLT-2074 Refactor desktop notification settings UI and add setting for duration (#3883)

* Refactor desktop notification settings UI and add setting for duration

* Update en.json

* Update desktop_notification_settings.jsx

webapp/actions/user_actions.jsx

@@ -81,4 +81,4 @@ function onThemeSaved(teamId, theme, onSuccess) {
     });
 
     onSuccess();
-}
+}