Update rubocop requirement from ~> 1.15.0 to ~> 1.23.0

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@v1.15.0...v1.23.0)

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

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

Author: dependabot[bot]

Gemfile

@@ -7,7 +7,7 @@ gem 'berkshelf'
 group :style do
   gem 'foodcritic', '~> 16.3.0'
   gem 'rake', '~> 13.0.1'
-  gem 'rubocop', '~> 1.15.0'
+  gem 'rubocop', '~> 1.23.0'
   gem 'rubocop-gitlab-security', '~> 0.1.1'
 end