[llvm] [Release] Add keith to valid archive uploaders (PR #106018)

[Keith Smiley via llvm-commits]

keith wrote:

Thanks for the info, I did see that (and am still curious about the path forward there) but actually I just wanted to upload a binary for 18.x since there haven't been consistent binaries for a while for macOS, and I was hoping to get one before that cutoff since it's unclear to me when folks will be able to get a new macOS binary given that change

https://github.com/llvm/llvm-project/pull/106018