Removes unused THCTensor_(triu), THCTensor_(div) (#34712)
Summary:
Per title. Dead code removal.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34712
Differential Revision: D20442618
Pulled By: mruberry
fbshipit-source-id: b03aa4984328f94021c1480e21375fd868d6d550
