Removed JsonSerializable (typeof (Rune)) per @bdisp

Terminal.Gui/Configuration/SourceGenerationContext.cs

@@ -20,6 +20,5 @@ namespace Terminal.Gui;
 [JsonSerializable (typeof (Dictionary<ColorName16, string>))]
 [JsonSerializable (typeof (Dictionary<string, ThemeScope>))]
 [JsonSerializable (typeof (Dictionary<string, ColorScheme>))]
-[JsonSerializable (typeof (Rune))]
 internal partial class SourceGenerationContext : JsonSerializerContext
 { }