[llvm] InstSimplify: strip bad TODO (NFC) (PR #92754)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Think about it. foldIdentityShuffles() requires two sets of canceling shuffles. If there are any intervening instructions, they are feeding in the result of the first set of shuffles. To eliminate the two sets of shuffles, you'd have to rewrite the head of the intervening instructions to feed in the operand of the first set of shuffles.

https://github.com/llvm/llvm-project/pull/92754