Bump rayon from 1.7.0 to 1.8.0 in /packer

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>

packer/Cargo.toml

@@ -19,7 +19,7 @@ anyhow = "^1"
 sha2 = "0.10.7"
 data-encoding = "^2"
 serde_json = "^1"
-rayon = "^1.7"
+rayon = "^1.8"
 indicatif = "^0.17"
 xz2 = "0.1.7"
 ignore = "0.4.20"