Update Rust crate toml to 0.8 (#121)

Co-authored-by: oxide-renovate[bot] <146848827+oxide-renovate[bot]@users.noreply.github.com>

Author: oxide-renovate[bot]

Cargo.lock

@@ -30,7 +30,7 @@ slog-term = "2.7"
 slog-async = "2.7"
 slog-envlogger = "2.2"
 propolis-client = { git = "https://github.com/oxidecomputer/propolis", rev = "ba4d338f0c98faa0328502c99aa6fa0e0948d3da" }
-toml = "0.7"
+toml = "0.8"
 libc = "0.2"
 tokio = { version = "1.44.2", features = ["full"] }
 tokio-tungstenite = "0.21"