[ValueTracking] Remove unused `V ^ Mask == C` from `computeKnownBitsFromCmp`. NFCI. (#125666)
I believe it is unused since we always convert it into `V == Mask ^ C`.
Code coverage:
https://dtcxzyw.github.io/llvm-opt-benchmark/coverage/data/zyw/opt-ci/actions-runner/_work/llvm-opt-benchmark/llvm-opt-benchmark/llvm/llvm-project/llvm/lib/Analysis/ValueTracking.cpp.html#L706