Merge pull request nwjs#2289 from jtg-gg/notification-disable-sound

[Notification] OSX, disable the default sound

Author: rogerwang

src/nw_notification_manager_mac.mm

@@ -132,7 +132,6 @@ -(void)userNotificationCenter:(NSUserNotificationCenter *)center didActivateNoti
     @"notification_id" :[NSNumber numberWithInt : params.notification_id],
   };
 
-  [notification setSoundName : @"NSUserNotificationDefaultSoundName"];
 
   [[NSUserNotificationCenter defaultUserNotificationCenter] setDelegate:[NWUserNotificationCenterDelegate defaultNWUserNotificationCenterDelegate]];