Remove `pytorch_linux_xenial_py3_5` build and test jobs (#35587)
Summary:
Because Python-3.5 is no longer supported on master
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35587
Differential Revision: D20718522
Pulled By: orionr
fbshipit-source-id: e8fdef044d8861fe062318c686215286fec3808b
