SeasonFinishWindow: Remove async from OnRenewContext() to avoid warnings

Elwig/Windows/SeasonFinishWindow.xaml.cs

@@ -19,8 +19,9 @@ namespace Elwig.Windows {
             SeasonInput.Value = Utils.CurrentLastSeason;
         }
 
-        protected override async Task OnRenewContext() {
+        protected override Task OnRenewContext() {
             SeasonInput_ValueChanged(null, null);
+            return Task.CompletedTask;
         }
 
         private async void SeasonInput_ValueChanged(object? sender, RoutedEventArgs? evt) {