fix labs warning in THVectorDefault.cpp (#19999)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19999
ghimport-source-id: 81157c60f0a9e5adbf12af8fc3a6e4352826b859
Differential Revision: D15169025
Pulled By: ljk53
fbshipit-source-id: 8e6f8df6dec6d21d6c7e743e974f4fcfff7cdeb5
