chore(deps-dev): update rubocop requirement from ~> 1.59.0 to ~> 1.60.0

Updates the requirements on [rubocop](https://github.com/rubocop/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.59.0...v1.60.0)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
...

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

propagator/xray/opentelemetry-propagator-xray.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'bundler', '~> 2.4'
   spec.add_development_dependency 'minitest', '~> 5.0'
   spec.add_development_dependency 'rake', '~> 13.0'
-  spec.add_development_dependency 'rubocop', '~> 1.59.0'
+  spec.add_development_dependency 'rubocop', '~> 1.60.0'
   spec.add_development_dependency 'rubocop-performance', '~> 1.20'
   spec.add_development_dependency 'simplecov', '~> 0.22.0'
   spec.add_development_dependency 'yard', '~> 0.9'