[clang] [clang][AST] fix ast-print of `extern <lang>` with >=2 declarators (PR #93131)

[Erich Keane via cfe-commits]

erichkeane wrote:

> What should be the next step following the approvals?

If you do not have 'squash and merge' rights here, one of us can do it for you once testing completes.

https://github.com/llvm/llvm-project/pull/93131