Remove definitions of acosh and asinh from TH (#28696)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28696
They are not used anywhere.
Test Plan: Imported from OSS
Differential Revision: D18302769
Pulled By: VitalyFedyunin
fbshipit-source-id: 8680951cbceb607ef545f92cbfa9204ce8f7ac4a
