Update nix requirement from 0.26.1 to 0.27.1

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@v0.26.1...v0.27.1)

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

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

Cargo.toml

@@ -62,7 +62,7 @@ warp = "0.3.1"
 
 # For testing unix signals
 [target.'cfg(unix)'.dev-dependencies]
-nix = { version = "0.26.1", default-features = false, features = ["signal"] }
+nix = { version = "0.27.1", default-features = false, features = ["signal"] }
 
 # Make leak sanitizer more reliable
 [profile.dev]