[clang] [clang][ObjectiveC] Fix Parsing the `::` Optional Scope Specifier (PR #119908)

[Fangrui Song via cfe-commits]

MaskRay wrote:

(https://discourse.llvm.org/t/hidden-emails-on-github-should-we-do-something-about-it/74223 the convention is to disable github's hide-email feature)

https://github.com/llvm/llvm-project/pull/119908