fix: Invalid debug-only message

Fixes the `The Bindable attribute is missing` message showing up in debug only configuration, reporting that types are not present in the generated bindable metadata.

src/SourceGenerators/Uno.UI.SourceGenerators/BindableTypeProviders/BindableTypeProvidersGenerationTask.cs

@@ -644,7 +644,7 @@ private void GenerateTypeTable(IndentedStringBuilder writer)
 					writer.AppendLineInvariant(@"#if DEBUG");
 					using (writer.BlockInvariant(@"lock(_knownMissingTypes)"))
 					{
-						using (writer.BlockInvariant(@"if(!_knownMissingTypes.Contains(type) && !type.IsGenericType)"))
+						using (writer.BlockInvariant(@"if(bindableType == null && !_knownMissingTypes.Contains(type) && !type.IsGenericType)"))
 						{
 							writer.AppendLineInvariant(@"_knownMissingTypes.Add(type);");
 							writer.AppendLineInvariant(@"Debug.WriteLine($""The Bindable attribute is missing and the type [{{type.FullName}}] is not known by the MetadataProvider. Reflection was used instead of the binding engine and generated static metadata. Add the Bindable attribute to prevent this message and performance issues."");");