
This fixes T86440 As the CU_2D flag is set for nurbs, a Curve can have 2D nurbs mixed with 3D. But the UI does not allow this mixing. It updates all nurbs to 2D or 3D when set. So remove this specific flag for nurbs. This may break old files, since 2D curves with mixed 3D are now set as 3D. Differential Revision: https://developer.blender.org/D10738