test_store multiworker remove multiprocessing (#59599)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59599
This will fix the flakiness for these tests internally when running under TSAN. We don't need multiprocessing since we should restrict the testing to the `wait_for_workers` and `world_size` parameters of the tcp store master store.
Test Plan: Imported from OSS
Reviewed By: mrshenli
Differential Revision: D28947838
Pulled By: H-Huang
fbshipit-source-id: d3e3904aa7ac81ae4c744a193a3b7167c2227bc8
