Updates deterministic flag to throw a warning, makes docs consistent (#45410)
Summary:
Per feedback in the recent design review. Also tweaks the documentation to clarify what "deterministic" means and adds a test for the behavior.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45410
Reviewed By: ngimel
Differential Revision: D23974988
Pulled By: mruberry
fbshipit-source-id: e48307da9c90418fc6834fbd67b963ba2fe0ba9d
