build(deps): bump darling from 0.20.11 to 0.21.3

Bumps [darling](https://github.com/TedDriggs/darling) from 0.20.11 to 0.21.3.
- [Release notes](https://github.com/TedDriggs/darling/releases)
- [Changelog](https://github.com/TedDriggs/darling/blob/master/CHANGELOG.md)
- [Commits](TedDriggs/darling@v0.20.11...v0.21.3)

---
updated-dependencies:
- dependency-name: darling
  dependency-version: 0.21.3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Cargo.lock

@@ -41,7 +41,7 @@ blake2 = { version = "0.10" }
 cargo_metadata = { version = "0.22.0" }
 cfg-if = { version = "1.0" }
 contract-build = { version = "6.0.0-beta" }
-darling = { version = "0.20.11" }
+darling = { version = "0.21.3" }
 derive_more = { version = "2.0.1", default-features = false }
 either = { version = "1.13", default-features = false }
 funty = { version = "2.0.0" }