Update rubocop requirement from ~> 1.1.0 to ~> 1.2.0

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.1.0...v1.2.0)

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

opt_parse_validator.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rake',                '~> 13.0'
   s.add_development_dependency 'rspec',               '~> 3.10.0'
   s.add_development_dependency 'rspec-its',           '~> 1.3.0'
-  s.add_development_dependency 'rubocop',             '~> 1.1.0'
+  s.add_development_dependency 'rubocop',             '~> 1.2.0'
   s.add_development_dependency 'rubocop-performance', '~> 1.8.0'
   s.add_development_dependency 'simplecov',           '~> 0.19.0'
   s.add_development_dependency 'simplecov-lcov',      '~> 0.8.0'