Add GDSOFTCLASS to deeper inheritors of Object

scene/3d/velocity_tracker_3d.h

@@ -33,6 +33,8 @@
 #include "core/object/ref_counted.h"
 
 class VelocityTracker3D : public RefCounted {
+	GDSOFTCLASS(VelocityTracker3D, RefCounted);
+
 	struct PositionHistory {
 		uint64_t frame = 0;
 		Vector3 position;