Update nix requirement from 0.30.1 to 0.31.1

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@v0.30.1...v0.31.1)

---
updated-dependencies:
- dependency-name: nix
  dependency-version: 0.31.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Cargo.toml

@@ -12,7 +12,7 @@ exclude = ["test_fixture"]
 
 [dependencies]
 libc = "0.2.158"
-nix = { version = "0.30.1", features = ["ioctl", "socket"] }
+nix = { version = "0.31.1", features = ["ioctl", "socket"] }
 
 [dev-dependencies]
 rand = "0.9.0"