Bump rayon from 1.8.0 to 1.8.1 (#13)

Bumps [rayon](https://github.com/rayon-rs/rayon) from 1.8.0 to 1.8.1.
- [Changelog](https://github.com/rayon-rs/rayon/blob/master/RELEASES.md)
- [Commits](https://github.com/rayon-rs/rayon/compare/rayon-core-v1.8.0...rayon-core-v1.8.1)

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

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

Cargo.toml

@@ -16,7 +16,7 @@ exclude = [
 clap = {version="3.2.25", features=['yaml']}
 error-chain = "0.12.0"
 rand = "0.8.*"
-rayon = "1.0.3"
+rayon = "1.8.1"
 
 [dev-dependencies]
 assert_approx_eq = "1.1.0"