App: Rename FocusPaymentVariantsWindow to FocusPaymentVariants

Elwig/Windows/SeasonFinishWindow.xaml.cs

@@ -119,7 +119,7 @@ namespace Elwig.Windows {
         private void PaymentButton_Click(object sender, RoutedEventArgs evt) {
             if (SeasonInput.Value is not int year)
                 return;
-            App.FocusPaymentVariantsWindow(year);
+            App.FocusPaymentVariants(year);
         }
     }
 }