Bump enumn from 0.1.5 to 0.1.8 (#7226)

Bumps [enumn](https://github.com/dtolnay/enumn) from 0.1.5 to 0.1.8.
- [Release notes](https://github.com/dtolnay/enumn/releases)
- [Commits](dtolnay/enumn@0.1.5...0.1.8)

---
updated-dependencies:
- dependency-name: enumn
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Cargo.lock

@@ -6,7 +6,7 @@ edition.workspace = true
 
 [dependencies]
 paste = "1.0"
-enumn = "0.1.5"
+enumn = "0.1.8"
 parity-scale-codec = { version = "3.4.0", default-features = false, features = ["derive"] }
 sp-std = { package = "sp-std", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }