[llvm] [NFC][LoopVectorize] Remove unused argument from fixupIVUsers (PR #109789)

[Matthew Devereau via llvm-commits]

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

If there's no unused argument in fixupIVUsers, then there's no argument from me.

https://github.com/llvm/llvm-project/pull/109789