[llvm] [ConstraintElim] Use isKnownNonNegative for signed->unsigned transfer. (PR #72879)

[Antonio Frighetto via llvm-commits]

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

LGTM, thanks! (Perhaps commit description can be generalized not only to SLT now, simplifyed -> simplified).

https://github.com/llvm/llvm-project/pull/72879