[gnome-control-center] notifications: Add help link

[Jeremy Bicha <jbicha src gnome org>]

commit eefc10dbe54e6afeda02e306fbeb6cf7db0a3a93
Author: Jeremy Bicha <jbicha ubuntu com>
Date:   Sun Oct 22 11:10:43 2017 -0400

    notifications: Add help link
    
    https://bugzilla.gnome.org/show_bug.cgi?id=789321

 panels/notifications/cc-notifications-panel.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)
---
diff --git a/panels/notifications/cc-notifications-panel.c b/panels/notifications/cc-notifications-panel.c
index 89e33e1..1265b5b 100644
--- a/panels/notifications/cc-notifications-panel.c
+++ b/panels/notifications/cc-notifications-panel.c
@@ -255,8 +255,7 @@ cc_notifications_panel_init (CcNotificationsPanel *panel)
 static const char *
 cc_notifications_panel_get_help_uri (CcPanel *panel)
 {
-  /* TODO */
-  return NULL;
+  return "help:gnome-help/shell-notifications";
 }
 
 static void