set workspace size to 4M (#74159)
Summary: Follow D34480690 (https://github.com/pytorch/pytorch/commit/3ec1dd9989ac5441c767f975f5e0fc46847400a2)
Test Plan: CI
Differential Revision: D34636039
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74159
Approved by: https://github.com/xuzhao9
