[llvm] [GlobalMerge][NFC] Skip sorting by profitability when it is not needed (PR #124146)

[Craig Topper via llvm-commits]

topperc wrote:

It's still not NFC with `>`. stable_sort won't change the order of equal elements. If there are multiple equal elements `reverse` would visit the later ones first. Removing the reverse means the earliest equal element first.

https://github.com/llvm/llvm-project/pull/124146