Update nix requirement from 0.30 to 0.31 (#7)

Author: dependabot[bot]

Cargo.toml

@@ -31,7 +31,7 @@ rand = "0.9"
 log = { version = "0.4", optional = true }
 
 [target.'cfg(unix)'.dependencies]
-nix = { version = "0.30", default-features = false, features = ["fs", "mman"] }
+nix = { version = "0.31", default-features = false, features = ["fs", "mman"] }
 libc = "0.2"
 
 [target.'cfg(windows)'.dependencies]