chore(deps): update frame-metadata requirement from 17.0.0 to 18.0.0

Updates the requirements on [frame-metadata](https://github.com/paritytech/frame-metadata) to permit the latest version.
- [Release notes](https://github.com/paritytech/frame-metadata/releases)
- [Changelog](https://github.com/paritytech/frame-metadata/blob/main/CHANGELOG.md)
- [Commits](paritytech/frame-metadata@v17.0.0...v18.0.0)

---
updated-dependencies:
- dependency-name: frame-metadata
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -14,7 +14,7 @@ exclude = ["/for_tests", "/.github"]
 [dependencies]
 bitvec = {version = "1.0.1", default-features = false, features = ["alloc"]}
 external-memory-tools = {version = "0.1.1", default-features = false}
-frame-metadata = {version = "17.0.0", default-features = false, features = ["current", "decode"]}
+frame-metadata = {version = "18.0.0", default-features = false, features = ["current", "decode"]}
 hex = {version = "0.4.3", default-features = false, features = ["alloc"]}
 num-bigint = {version = "0.4.6", default-features = false}
 plot_icon = {version = "0.3.0", optional = true, default-features = false, features = ["pix"]}