Update the `gix` family of crates to avoid the vulnerability reported in
[CVE-2025-31130].
Since `gix-hash` is used in two places, its version definition was moved to the
top-level `Cargo.toml`. `cargo` warned that `default-features` not being defined
in the top-level could result in a future error, so that was carried along with
it. This did not affect the build of `radicle-fetch`.
[CVE-2025-31130]: https://www.cve.org/CVERecord?id=CVE-2025-31130
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