[llvm] [CodeGen] Get rid of incorrect `std` template specializations (PR #160804)

[via llvm-commits]

YexuanXiao wrote:

I approve this change. The stateful specialization of `std::less<>` affects all downstream users who expect it to behave like the primary template, so it should be avoided.

https://github.com/llvm/llvm-project/pull/160804