In the NotificationObject class is an incorrectly text set in the obsolete attribute.
Wrong
[Obsolete("Please use Prism.PubSubEvents.PubSubEvent.")]
Right
[Obsolete("Please use Prism.Mvvm.BindableBase.")]
Wrong
[Obsolete("Please use Prism.PubSubEvents.PubSubEvent.")]
Right
[Obsolete("Please use Prism.Mvvm.BindableBase.")]