Update rubocop requirement from ~> 1.21.0 to ~> 1.22.0

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@v1.21.0...v1.22.0)

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

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

Gemfile

@@ -13,7 +13,7 @@ group :development do
   gem 'rake',                  '~> 13.0'
   gem 'rspec',                 '~> 3.0'
   gem 'rspec-benchmark',       '~> 0.6.0'
-  gem 'rubocop',               '~> 1.21.0'
+  gem 'rubocop',               '~> 1.22.0'
   gem 'rubocop-performance',   '~> 1.11.5'
   gem 'rubocop-rspec',         '~> 2.4.0'
   gem 'simplecov',             ['>= 0.18.0', '< 0.22.0']