DeepSpeed

a74a604a - Revert "Activation checkpointing bugfix and unit tests (#420)" (#422)

Revert "Activation checkpointing bugfix and unit tests (#420)" (#422) This reverts commit 01b6e27e7833a2ac3b415b03674ef11116078e9c. Co-authored-by: Shaden Smith <ShadenTSmith@gmail.com>