Update nix requirement from 0.26.2 to 0.28.0

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@v0.26.2...v0.28.0)

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

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

Author: dependabot[bot]

Cargo.toml

@@ -14,7 +14,7 @@ readme = "README.md"
 log = "0.4.20"
 anyhow = "1.0.75"
 rust-embed = "8.0.0"
-nix = { version = "0.26.2", features = ["mount", "signal", "user"]}
+nix = { version = "0.28.0", features = ["mount", "signal", "user"]}
 rand = "0.8.5"
 ureq = "2.7.1"
 indicatif = "0.17.6"