[clang] [Clang][AST][NFC] Correct Comment in GenericSelectionExpr (PR #180850)

[Will Hawkins via cfe-commits]

hawkinsw wrote:

> > Just wanted to wait for @riccibruno to sign off before merging!!
> 
> FWIW, I've not seen that user active in quite some time, so I don't think they'll come around to sign off; no need to wait to land.

Thanks!! I just landed it. `/me` hopes he didn't screw something up!

https://github.com/llvm/llvm-project/pull/180850