About FortiOS 5.6.2 registration-notification command

Hello, I have a problem with fortiOS 5.6.2

I don't want see the registration notification when every time I login.

Before, with fortiOS 5.4, I can use the command below to disable the notification

config system global

  set registration-notification disable

now I can't type this command on fortiOS 5.6.2, seems it don't have this command.

If anyone can help me about this problem.