chore(deps): update nix requirement from 0.28 to 0.29

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@v0.28.0...v0.29.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

phantun/Cargo.toml

@@ -21,4 +21,4 @@ pretty_env_logger = "0.5"
 tokio-tun = "0.11"
 num_cpus = "1.13"
 neli = "0.6"
-nix = { version = "0.28", features = ["net"] }
+nix = { version = "0.29", features = ["net"] }