Fix build failure due to namespace change for log_out and tanh_out (#56278)
Summary:
There is a build failure in `bench_approx.cpp` due to namespace change for log_out and tanh_out.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56278
Reviewed By: bertmaher, nikithamalgifb
Differential Revision: D27825621
Pulled By: navahgar
fbshipit-source-id: 0bccd324af92a3460610bf475514449f0223de2b
