Update dependency rubocop-rspec to '~> 3.4.0'

Author: renovate[bot]

Diff for: cucumber.gemspec

@@ -44,7 +44,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rubocop-capybara', '~> 2.21.0'
   s.add_development_dependency 'rubocop-packaging', '~> 0.5.2'
   s.add_development_dependency 'rubocop-rake', '~> 0.6.0'
-  s.add_development_dependency 'rubocop-rspec', '~> 3.3.0'
+  s.add_development_dependency 'rubocop-rspec', '~> 3.4.0'
   s.add_development_dependency 'simplecov', '~> 0.22.0'
   s.add_development_dependency 'webrick', '~> 1.8'