Revert "Add mkl implementation for exponential on CPU (#69967)"
This reverts commit 189768ed64561e61ff05c9e42adfa40139388204.
Reverted https://github.com/pytorch/pytorch/pull/69967 on behalf of https://github.com/izaitsevfb due to This PR caused internal breakage (internal revert D39348330; relevant task T131416326)
