Bump num_cpus from 1.14.0 to 1.15.0 in /ruby

Bumps [num_cpus](https://github.com/seanmonstar/num_cpus) from 1.14.0 to 1.15.0.
- [Release notes](https://github.com/seanmonstar/num_cpus/releases)
- [Changelog](https://github.com/seanmonstar/num_cpus/blob/master/CHANGELOG.md)
- [Commits](seanmonstar/num_cpus@v1.14.0...v1.15.0)

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

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

Author: dependabot[bot]

ruby/Cargo.lock

@@ -16,7 +16,7 @@ clap = "3.0"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3.3", features = ["env-filter"] }
 rayon = "1.5.0"
-num_cpus = "1.14.0"
+num_cpus = "1.15.0"
 regex = "1.7.1"
 encoding = "0.2"
 lazy_static = "1.4.0"