Update Rust crate zone to 0.3.1

Author: oxide-renovate[bot]

Diff for: Cargo.toml

@@ -18,7 +18,7 @@ members = [
 [workspace.dependencies]
 thiserror = "1.0"
 anyhow = "1.0"
-zone = "0.3.0"
+zone = "0.3.1"
 regex = "1.5"
 smf = "0.2"
 libnet = { git = "https://github.com/oxidecomputer/netadm-sys", branch = "main" }