Update voxpupuli-rubocop requirement from ~> 1.1 to ~> 2.0

Updates the requirements on [voxpupuli-rubocop](https://github.com/voxpupuli/voxpupuli-rubocop) to permit the latest version.
- [Changelog](https://github.com/voxpupuli/voxpupuli-rubocop/blob/master/CHANGELOG.md)
- [Commits](voxpupuli/voxpupuli-rubocop@v1.1.0...v2.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile

@@ -17,5 +17,5 @@ group :development do
   gem 'rspec', '~> 3.12'
   gem 'rspec-collection_matchers', '~> 1.2'
   gem 'rspec-its', '~> 1.3'
-  gem 'voxpupuli-rubocop', '~> 1.1'
+  gem 'voxpupuli-rubocop', '~> 2.0'
 end