Update rubocop requirement from = 1.26.1 to = 1.27.0

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@v1.26.1...v1.27.0)

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

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

rubocop-govuk.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "rake", "~> 13"
 
-  spec.add_dependency "rubocop", "1.26.1"
+  spec.add_dependency "rubocop", "1.27.0"
   spec.add_dependency "rubocop-ast", "1.16.0"
   spec.add_dependency "rubocop-rails", "2.14.2"
   spec.add_dependency "rubocop-rake", "0.6.0"