Update strum_macros requirement from 0.23.1 to 0.24.0

Updates the requirements on [strum_macros](https://github.com/Peternator7/strum) to permit the latest version.
- [Release notes](https://github.com/Peternator7/strum/releases)
- [Changelog](https://github.com/Peternator7/strum/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Peternator7/strum/commits)

---
updated-dependencies:
- dependency-name: strum_macros
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

chain-impl-mockchain/Cargo.toml

@@ -18,7 +18,7 @@ rand_core = "0.6"
 imhamt = { path = "../imhamt" }
 sparse-array = { path = "../sparse-array" }
 strum = "0.23.0"
-strum_macros = "0.23.1"
+strum_macros = "0.24.0"
 hex = { version = "0.4.2", default-features = false, features = [ "std" ] }
 quickcheck = { version = "0.9", optional = true }
 quickcheck_macros = { version = "0.9", optional = true }