[llvm] [SCEV] Avoid erase+insert in constant folding (NFC) (PR #101642)

[Nikita Popov via llvm-commits]

nikic wrote:

@fhahn Hm, now that I think about it, the change is not strictly NFC, because it may change the order of operands (as we swap instead of erase+insert) and complexity sorting uses a partial order. 

https://github.com/llvm/llvm-project/pull/101642