Normals no longer export

[dgovil]

This PR #2713 introduced a fairly large breaking change IMHO that removes normals from exports if subdivision scheme is set to None.

Per the USD spec, having subdivision schema set to None should mean that it's a raw polygonal mesh, and normals should be exported if that's the case.

I'd really like to request that the behavior in that PR be either reverted OR that more reasoning be given, so that people can adjust their pipelines accordingly. The current behaviour unfortunately is what I would consider a breaking change for most pipelines that aren't using subdivision surfaces (games, realtime etc)....

[dgovil]

I made a PR here to resolve this and fix the documentation #2768

[santosd]

Looks like #2713 will be reverted and documentation will be updated. Thank you @dgovil for bringing this up.