Bump rayon from 1.7.0 to 1.8.0 (#985)

Bumps [rayon](https://github.com/rayon-rs/rayon) from 1.7.0 to 1.8.0.
- [Changelog](https://github.com/rayon-rs/rayon/blob/master/RELEASES.md)
- [Commits](rayon-rs/rayon@rayon-core-v1.7.0...rayon-core-v1.8.0)

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

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

Cargo.toml

@@ -33,7 +33,7 @@ numpy = "0.19.0"
 petgraph = "0.6.4"
 rand = "0.8"
 rand_pcg = "0.3"
-rayon = "1.7"
+rayon = "1.8"
 rayon-cond = "1.7"
 
 [lib]