proto: Remove `GetPrivateUserInfo` message (#36265)

This PR removes the `GetPrivateUserInfo` RPC message.

We're no longer using the message after
https://github.com/zed-industries/zed/pull/36255.

Release Notes:

- N/A
bd1fda6782Marshall Bowers committed on 8/15/2025, 6:27:31 PM· committed by GitHubparente452aba
5 files changedLine totals unavailable