Windows: Remove SeasonFinishWindow and TestWindow

Elwig/App.xaml.cs

@@ -273,10 +273,6 @@ namespace Elwig {
             return w;
         }
 
-        public static SeasonFinishWindow FocusSeasonFinish() {
-            return FocusWindow<SeasonFinishWindow>(() => new());
-        }
-
         public static OriginHierarchyWindow FocusOriginHierarchy() {
             return FocusWindow<OriginHierarchyWindow>(() => new());
         }