[llvm] [DominanceFrontierBase] Fix doc of compare()'s return value. (PR #81352)

[Florian Hahn via llvm-commits]

fhahn wrote:

LGTM, thanks! Adjusted the title to be a bit more concise.

It indeed appears as if the function isn't used and IMO it should probably be removed.

https://github.com/llvm/llvm-project/pull/81352