Delete dead code in THTensorMoreMath.cpp (#17993)

Delete dead code in THTensorMoreMath.cpp (#17993)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17993
ghimport-source-id: 5427773f6306bdeddffd9a3ae032acc3f253f458

Stack:
* #17926 Implement at::has_internal_overlap helper function
* #17927 Error out on in-place (unary) ops on tensors that have internal overlap
* **#17993 [easy] Delete dead code in THTensorMoreMath.cpp**

We seem to have new implementations already for these in ATen.

Reviewed By: ezyang

Differential Revision: D14457838

fbshipit-source-id: 8481aad74b2127bd28c0f3e09740889fc0488a31