Don't disable `Material` and `PlaceholderMaterial` when `disable_3d=yes`

(cherry picked from commit 1f1be5fe9b11093d3aeb955d4fbd28325f4c5e56)

scene/register_scene_types.cpp

@@ -695,6 +695,8 @@ void register_scene_types() {
 	GDREGISTER_CLASS(VisualShaderNodeParticleAccelerator);
 	GDREGISTER_CLASS(VisualShaderNodeParticleEmit);
 
+	GDREGISTER_VIRTUAL_CLASS(Material);
+	GDREGISTER_CLASS(PlaceholderMaterial);
 	GDREGISTER_CLASS(ShaderMaterial);
 	GDREGISTER_ABSTRACT_CLASS(CanvasItem);
 	GDREGISTER_CLASS(CanvasTexture);
@@ -802,11 +804,9 @@ void register_scene_types() {
 	GDREGISTER_CLASS(TubeTrailMesh);
 	GDREGISTER_CLASS(RibbonTrailMesh);
 	GDREGISTER_CLASS(PointMesh);
-	GDREGISTER_VIRTUAL_CLASS(Material);
 	GDREGISTER_ABSTRACT_CLASS(BaseMaterial3D);
 	GDREGISTER_CLASS(StandardMaterial3D);
 	GDREGISTER_CLASS(ORMMaterial3D);
-	GDREGISTER_CLASS(PlaceholderMaterial);
 	GDREGISTER_CLASS(ProceduralSkyMaterial);
 	GDREGISTER_CLASS(PanoramaSkyMaterial);
 	GDREGISTER_CLASS(PhysicalSkyMaterial);