Fixed another missing property change notification

Author: Sergio0694

Microsoft.Toolkit.Mvvm/Input/AsyncRelayCommand{T}.cs

@@ -191,6 +191,7 @@ public void Cancel()
             this.cancellationTokenSource?.Cancel();
 
             OnPropertyChanged(AsyncRelayCommand.IsCancellationRequestedChangedEventArgs);
+            OnPropertyChanged(AsyncRelayCommand.CanBeCanceledChangedEventArgs);
         }
     }
 }