Update on "Enable fused optimizer for DP"

Differential Revision: [D42714482](https://our.internmc.facebook.com/intern/diff/D42714482/)

**NOTE FOR REVIEWERS**: This PR has internal Meta-specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D42714482/)!

[ghstack-poisoned]

torch/csrc/distributed/c10d/reducer.cpp

@@ -1466,7 +1466,7 @@ void Reducer::finalize_bucket_dense(Bucket& bucket) {
     if (!gradient_as_bucket_view_) {
       if (optim_in_backward_) {
         // Return early if optimizer has already run.
-        runGradCallbackForVariable(variable, [&](auto& grad) {return true;});
+        runGradCallbackForVariable(variable, [&](auto& grad) { return true; });
       } else {
         RECORD_FUNCTION(
             "torch.distributed.ddp.reducer::copy_bucket_to_grad",