Update nix requirement from 0.29.0 to 0.30.0 (#344)

Updates the requirements on [nix](https://github.com/nix-rust/nix) to permit the latest version.
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](nix-rust/nix@v0.29.0...v0.30.0)

---
updated-dependencies:
- dependency-name: nix
  dependency-version: 0.30.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Cargo.toml

@@ -62,7 +62,7 @@ serde_urlencoded = { version = "0.7", optional = true }
 tokio = { version = "1.29.0", features = ["sync", "macros", "rt", "time", "io-util"] }
 
 [target.'cfg(target_family="unix")'.dev-dependencies]
-nix = { version = "0.29.0", features = ["fs"] }
+nix = { version = "0.30.0", features = ["fs"] }
 
 [target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies]
 web-time = { version = "1.1.0" }