Remove unneeded TODO (pytorch#80453)

This TODO is no longer needed, as we use `_register_fused_optim` to register the overlapped optimizer in DDP.  Also, remove comment about API being experimental, as this API is no longer going to be used by end user.
Pull Request resolved: pytorch#80453
Approved by: https://github.com/awgu

torch/distributed/algorithms/ddp_comm_hooks/optimizer_overlap_hooks.py

@@ -30,16 +30,12 @@ def _check_valid_functional_optim(self):
             )
 
 
-# TODO: Add an example to use such a wrapper.
 def _hook_then_optimizer(
     hook: Callable[[Any, dist.GradBucket], torch.futures.Future[torch.Tensor]],
     optimizer_state: _OptimizerHookState,
 ) -> Callable[[Any, dist.GradBucket], torch.futures.Future[torch.Tensor]]:
     r"""
     Runs optimizer in a functional fashion after DDP communication hook.
-
-    .. warning ::
-        This API is experimental adn subject to change.
     """
     has_set_params = (
         hasattr(optimizer_state, 'params_to_optimize')