build(deps): bump num_cpus from 1.14.0 to 1.15.0 (#4265)

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>

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

graph/Cargo.toml

@@ -25,7 +25,7 @@ futures = "0.1.21"
 graphql-parser = "0.4.0"
 lazy_static = "1.4.0"
 num-bigint = { version = "^0.2.6", features = ["serde"] }
-num_cpus = "1.14.0"
+num_cpus = "1.15.0"
 num-traits = "0.2.15"
 rand = "0.8.4"
 regex = "1.5.4"