[clang] [clang-tools-extra] [clang] Make `InitListExpr::isExplicit()` work (PR #195175)

[Andrey Ali Khan Bolshakov via cfe-commits]

https://github.com/bolshakov-a commented:

@AaronBallman, @erichkeane, @cor3ntin, @llvm-beanz, @svenvh, @Sirraide, @Fznamznon

https://github.com/llvm/llvm-project/pull/195175