[ZeroRedundancyOptimizer] Remove pseudo futures handling, not needed (#52698)
Summary:
This was mostly needed for ShardedDDP, not used here, dead code removal
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52698
Reviewed By: mrshenli
Differential Revision: D26617893
Pulled By: blefaudeux
fbshipit-source-id: 9bcfca5135bf332ebc1240300978c138d2041146
