cleanup: Remove trailing spaces

We generally avoid these (not least because Linus hates them enough
to make git complain loudly), but some sneaked in over time ...

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/731

js/ui/notificationDaemon.js

@@ -618,7 +618,7 @@ function getPlatformData() {
 
 function InvalidAppError() {}
 
-var GtkNotificationDaemonAppSource = 
+var GtkNotificationDaemonAppSource =
 class GtkNotificationDaemonAppSource extends MessageTray.Source {
     constructor(appId) {
         let objectPath = objectPathFromAppId(appId);