[tensorexpr] Remove the optional argument in LoopNest::prepareForCodeGen (#67144)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/67144
Test Plan: Imported from OSS
Reviewed By: ZolotukhinM
Differential Revision: D31881150
Pulled By: huiguoo
fbshipit-source-id: af99087722ec71d6deb9049b63b573ae7720c9ec
