chore: Update rubocop requirement from = 1.58.0 to = 1.59.0 (#1008)

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@v1.58.0...v1.59.0)

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

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appium_lib.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'posix-spawn', '~> 0.3'
   s.add_development_dependency 'pry'
   s.add_development_dependency 'rake', '~> 13.0'
-  s.add_development_dependency 'rubocop', '1.58.0'
+  s.add_development_dependency 'rubocop', '1.59.0'
   s.add_development_dependency 'spec', '~> 5.3', '>= 5.3.4'
   s.add_development_dependency 'yard', '~> 0.9.11'