[clang] [Clang] Fix handling of placeholder variables name in init captures (PR #107055)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 approved this pull request.

One thing I'm not entirely clear about is why we would end up with two same placeholder `Decl`s in `LookupResult`.

It seems that `IdResolver` results in two same duplicate Decls for such case, but I don't know why.

(However I'd still approve it because this reverts the condition to the state before the placeholder patch.)

https://github.com/llvm/llvm-project/pull/107055