Kill Backend constructor of TensorOptions. (#18137)
Summary:
It's wrong and unused. Use one of the many other constructors instead :).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18137
Differential Revision: D14508364
Pulled By: gchanan
fbshipit-source-id: 19c6ff78ad9d9221d0874425edd02b78627c4ca7
