Update rubocop requirement from ~> 1.63.0 to ~> 1.64.0 (#65)

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@v1.63.0...v1.64.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

@@ -17,7 +17,7 @@ group :development_test do
 end
 
 group :development_lint do
-  gem 'rubocop', '~> 1.63.0', require: false
+  gem 'rubocop', '~> 1.64.0', require: false
 end
 
 group :development_local do