Fix gltf importer forcing vertex colors on all materials

The importer already checks if a mesh has vertex colors and enables
vertex colors on the material using it.

Before this fix, GLTF importer would force shader generation to use
vertex colors even if the scene did not have vertex colors at all, or
did not need them; causing inefficient shader and PSO generation.

modules/gltf/gltf_document.cpp

@@ -3877,7 +3877,6 @@ Error GLTFDocument::_parse_materials(Ref<GLTFState> p_state) {
 		} else {
 			material->set_name(vformat("material_%s", itos(i)));
 		}
-		material->set_flag(BaseMaterial3D::FLAG_ALBEDO_FROM_VERTEX_COLOR, true);
 		Dictionary material_extensions;
 		if (material_dict.has("extensions")) {
 			material_extensions = material_dict["extensions"];