Optimize Install dependencies phase of MacOS runner in Github Actions.

[rasswanth-s]

Description

The install dependencies section of MacOS runner in CI consumes a considerable amount of time.The pip cache also caches the dependencies.One aspect of optimization is to look at the cache mises while installing.

Additional Context

Mac OS CI run : https://github.com/OpenMined/SyMPC/runs/3277453139?check_suite_focus=true
Ubuntu OS CI run : https://github.com/OpenMined/SyMPC/runs/3277453119?check_suite_focus=true