radicle/git/raw: `Config` not used on Windows — heartwood

Fix a clippy lint that sneaked in…

 // Re-exports that are only used within this crate.
 pub(crate) use git2::{
     message_trailers_strs, AutotagOption, Blob, Config, FetchOptions, FetchPrune, Object, Revwalk,
     Sort,
     message_trailers_strs, AutotagOption, Blob, FetchOptions, FetchPrune, Object, Revwalk, Sort,
 };
 #[cfg(unix)]
 pub(crate) use git2::Config;
 // Re-exports that are only used within this crate for testing.
 #[cfg(any(test, feature = "test"))]
 pub(crate) use git2::RemoteCallbacks;