Update rubocop requirement from ~> 1.58.0 to ~> 1.59.0

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@v1.58.0...v1.59.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

checkstyle-suppression-generator.gemspec

@@ -25,6 +25,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'mocha', '~> 2.1.0'
   s.add_development_dependency 'pry-byebug', '~> 3.10.1'
   s.add_development_dependency 'rake', '~> 13.1.0'
-  s.add_development_dependency 'rubocop', '~> 1.58.0'
+  s.add_development_dependency 'rubocop', '~> 1.59.0'
   s.add_development_dependency 'simplecov', '~> 0.22.0'
 end