Remove THSTensor and SparseTensorRef (#20877)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20877
ghimport-source-id: a07f53ca158f9a3dce7a25ef5a169871e98ea3ea
Differential Revision: D15480353
Pulled By: li-roy
fbshipit-source-id: 1152dbc4df827ded3be1a57f007a6b7de12f567f
