Update nix requirement from 0.21 to 0.22

Updates the requirements on [nix](https://github.com/nix-rust/nix) to permit the latest version.
- [Release notes](https://github.com/nix-rust/nix/releases)
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](https://github.com/nix-rust/nix/commits)

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

Signed-off-by: dependabot[bot] <support@github.com>

acmed/Cargo.toml

@@ -33,7 +33,7 @@ tinytemplate = "1.2"
 toml = "0.5"
 
 [target.'cfg(unix)'.dependencies]
-nix = "0.21"
+nix = "0.22"
 
 [build-dependencies]
 serde = { version = "1.0", features = ["derive"] }