Update on "[Gradient Compression] Change wait() to value() in some ca…

…llbacks of PowerSGD communication hook"


Since wait() has already been called in the return statements of the precursor callbacks, no need to wait again.

Original PR issue: Investigate Applying PowerSGD to Communication Hook for Gradient Compression #47202

Differential Revision: [D25672068](https://our.internmc.facebook.com/intern/diff/D25672068/)

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