[gnome-shell] messageTray: Remove unused source object parameter

[Florian Müllner <fmuellner src gnome org>]

commit 72566eda43b97129b30916fe20750df50f7b6fb0
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Jul 12 14:58:42 2019 +0200

    messageTray: Remove unused source object parameter
    
    This is has been added in commit b150869b5 but is never used
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/700

 js/ui/messageTray.js | 1 -
 1 file changed, 1 deletion(-)
---
diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index 4e1841fc00..6a65d5febf 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -1004,7 +1004,6 @@ var MessageTray = class MessageTray {
 
     _addSource(source) {
         let obj = {
-            source: source,
             notifyId: 0,
             destroyId: 0,
         };