Fix nested GodotObject class in generic class lead to source generator errors in C#

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/Sources/NestedInGeneric.cs

@@ -0,0 +1,9 @@
+using Godot;
+
+public partial class GenericClass<T>
+{
+	public partial class NestedClass : GodotObject
+	{
+
+	}
+}