[llvm] [NFC][CodingStandard] Require``[[maybe_unused]]`` for unused variables in asserts (PR #142850)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Thanks. @nikic and/or @AaronBallman if one of you can approve as well, I will go ahead and merge it. Thanks!

https://github.com/llvm/llvm-project/pull/142850