Update rubocop requirement from ~> 1.31.0 to ~> 1.64.1

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@v1.31.0...v1.64.1)

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

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

skylight.gemspec

@@ -37,7 +37,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake-compiler", "~> 1.2.0"
   spec.add_development_dependency "rspec", "~> 3.7"
   spec.add_development_dependency "rspec-collection_matchers", "~> 1.1"
-  spec.add_development_dependency "rubocop", "~> 1.31.0"
+  spec.add_development_dependency "rubocop", "~> 1.64.1"
   spec.add_development_dependency "simplecov", "~> 0.21.2"
   spec.add_development_dependency "syntax_tree"
   spec.add_development_dependency "timecop", "~> 0.9"