[llvm] [ConstantFolding] Consider `tanh*` to always be a noop (PR #70794)

[Shivam Gupta via llvm-commits]

xgupta wrote:

> I've reverted this given it broke `check-llvm`. If we're going to land old PRs we should probably rerun premerge CI.
> 
> Also, @xgupta, please stop approving and merging 2-3 year old PRs. It is unclear if any of them are still needed.

Sorry I should have run it locally once. I will make sure from next time.  Thanks for the revert. 

https://github.com/llvm/llvm-project/pull/70794