Update rubocop requirement from = 1.56.4 to = 1.57.1

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@v1.56.4...v1.57.1)

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

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

ridgepole.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec', '>= 3.0.0'
   spec.add_development_dependency 'rspec-match_fuzzy', '>= 0.1.3'
   spec.add_development_dependency 'rspec-match_ruby', '>= 0.1.3'
-  spec.add_development_dependency 'rubocop', '1.56.4'
+  spec.add_development_dependency 'rubocop', '1.57.1'
   spec.add_development_dependency 'rubocop-rake', '>= 0.5.1'
   spec.add_development_dependency 'rubocop-rspec', '>= 2.1.0'
   spec.add_development_dependency 'simplecov'