Update rubocop requirement from 1.63.5 to 1.64.0

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@v1.63.5...v1.64.0)

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

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

gemfiles/base.gemfile

@@ -6,7 +6,7 @@ gem 'redis', require: false
 gem 'rspec', '>= 3.7.0'
 gem 'rspec-collection_matchers'
 gem 'rspec-its'
-gem 'rubocop', '1.63.5'
+gem 'rubocop', '1.64.0'
 gem 'sqlite3', '~> 1.4'
 gem 'timecop'
 gem 'unparser'