Update Rust crate num_enum to 0.7.4 (#511)

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

Author: oxide-renovate[bot]

Cargo.lock

@@ -69,7 +69,7 @@ ctrlc = { version = "3.4.7", features = ["termination"] }
 ztest = { git = "https://github.com/oxidecomputer/falcon", branch = "main" }
 anstyle = "1.0.11"
 nom = "7.1"
-num_enum = "0.7.3"
+num_enum = "0.7.4"
 pretty-hex = "0.4"
 pretty_assertions = "1.4"
 lazy_static = "1.4"