Yes, you will need to remove the OnNotificationStopDisplay binding, assuming it’s possible for the notifications to ever call that multiple times.
It may be best to add a dedicated callback function that OnNotificationStopDisplay binds to instead of just binding directly to TryToInvokeNotification. For that dedicated callback function, the notification could pass a reference to self. There you could remove the binding and then call TryToInvokeNotification().
That’s the type of reason largely every unreal C++ delegate passes a reference to self.