remove data manager

OwnChar.App.Desktop/UI/Windows/MainWindow.cs

@@ -18,7 +18,6 @@ namespace OwnChar.App.Desktop.UI.Windows
     public partial class MainWindow : RadTabbedForm
     {
         private readonly OwnCharManager manager = new();
-        private readonly IDataManager dataManager = new DefaultDataManager(new JsonFileDataProvider("test.json"));
 
         public MainWindowApi Api { get; }