[PyTorch] Remove dead get/setTLSCallbacks APIs (#56492)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56492
These are documented as internal-only and aren't called.
ghstack-source-id: 128354112
Test Plan: CI
Reviewed By: ilia-cher
Differential Revision: D27834789
fbshipit-source-id: 4a1aa320f952249db51945ff77563558fa884266
