Deprecate torch.autograd.function.traceable, is_traceable (#121413)
- There are no usages of this internally.
- There are very few usages of this in OSS (most of these are forks of old
repositories).
- This flag doesn't do anything.
We're deprecating it to prevent confusion. I will delete it immediately
after the branch cut.
Test Plan:
- new tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121413
Approved by: https://github.com/albanD, https://github.com/soulitzer
