[pytorch][codegen] remove dead code in gen_variable_type.py (#47975)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47975
Test Plan: Imported from OSS
Reviewed By: ezyang
Differential Revision: D24976274
Pulled By: ljk53
fbshipit-source-id: 8542471ee30f26592aad949fc17eef87a47df024
