[llvm] [NewPM] Remove LowerWidenableConditionLegacyPass (PR #72818)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM

> Not sure if this one would be good to land as the Lower* passes are used quite often in the Backend, and even though it's used upstream, it might b be used somewhere downstream?

Azul confirmed in https://reviews.llvm.org/D153677#4452433 that they're not using this in the backend, so I think we can go ahead and remove this. If it turns out that someone else is using it in the backend, we should revert the patch later.

https://github.com/llvm/llvm-project/pull/72818