[llvm] [DomTree] Remove unnecessary domtree level check in SemiNCA (NFC) (PR #73107)

[Jakub Kuderski via llvm-commits]

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

LGTM, but I would be more confident if we could wait for a confirmation that this `if` body is dead in some fleed-wide profile.

https://github.com/llvm/llvm-project/pull/73107