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

[Tobias Hieta via llvm-commits]

tru wrote:

Thanks for offering @keith  - but I think after the recent [RFC](https://discourse.llvm.org/t/rfc-improve-binary-security/78121?u=tobiashieta) we probably don't want to have manually uploaded binaries except from the bots. You are free to start uploading the binaries to the third-party binaries thread and hopefully we can get some official macOS binaries later.

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