Update cargo_metadata requirement from ^0.19 to ^0.21

Updates the requirements on [cargo_metadata](https://github.com/oli-obk/cargo_metadata) to permit the latest version.
- [Release notes](https://github.com/oli-obk/cargo_metadata/releases)
- [Changelog](https://github.com/oli-obk/cargo_metadata/blob/main/CHANGELOG.md)
- [Commits](oli-obk/cargo_metadata@0.19.0...0.21.0)

---
updated-dependencies:
- dependency-name: cargo_metadata
  dependency-version: 0.21.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Cargo.toml

@@ -16,7 +16,7 @@ crossbeam = "^0.8.2"
 tracing = "^0.1"
 tracing-subscriber = { version = "^0.3", features = ["env-filter"] }
 rayon = "^1.8.0"
-cargo_metadata = "^0.19"
+cargo_metadata = "^0.21"
 minijinja = { version = "^2.0", features = ["loader"] }
 
 [dev-dependencies]