Install sympy (#1347)
Summary:
Building torchdata requires sympy.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1347
Test Plan: https://github.com/pytorch/benchmark/actions/runs/3707183290
Reviewed By: davidberard98
Differential Revision: D42080648
Pulled By: xuzhao9
fbshipit-source-id: a02a231d8eb84cd057d13dae9020a4fa1c3fc0e8
