cleanup: Don't shadow variables

Having variables that share the same name in overlapping scopes is
confusing and error-prone, and is best avoided.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/805

js/ui/windowAttentionHandler.js

@@ -48,7 +48,7 @@ var WindowAttentionHandler = class {
         source.showNotification(notification);
 
         source.signalIDs.push(window.connect('notify::title', () => {
-            let [title, banner] = this._getTitleAndBanner(app, window);
+            [title, banner] = this._getTitleAndBanner(app, window);
             notification.update(title, banner);
         }));
     }