chore: Update rubocop requirement from = 1.67.0 to = 1.68.0 (#1043)

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@v1.67.0...v1.68.0)

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

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

appium_lib.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'minitest-reporters', '~> 1.1'
   s.add_development_dependency 'pry'
   s.add_development_dependency 'rake', '~> 13.0'
-  s.add_development_dependency 'rubocop', '1.67.0'
+  s.add_development_dependency 'rubocop', '1.68.0'
   s.add_development_dependency 'yard', '~> 0.9.11'
 
   s.files = `git ls-files`.split("\n").reject { |v| v.match(/\A^(ios_tests|android_tests|grid|test_apps)\/.+/) }