Update rubocop requirement from ~> 0.60.0 to ~> 0.61.0

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](https://github.com/rubocop-hq/rubocop/commits/v0.61.0)

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

dependabot-core.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec", "~> 3.8.0"
   spec.add_development_dependency "rspec-its", "~> 1.2.0"
   spec.add_development_dependency "rspec_junit_formatter", "~> 0.4"
-  spec.add_development_dependency "rubocop", "~> 0.60.0"
+  spec.add_development_dependency "rubocop", "~> 0.61.0"
   spec.add_development_dependency "vcr", "~> 4.0.0"
   spec.add_development_dependency "webmock", "~> 3.4.0"