remove some more rubocop

Author: jcupitt

Rakefile

@@ -25,9 +25,3 @@ unless RUBY_PLATFORM.include?("java")
 
   YARD::Rake::YardocTask.new
 end
-
-# RuboCop requires Ruby >= 2.2
-if Gem.ruby_version >= Gem::Version.new("2.2.0")
-  require "rubocop/rake_task"
-  RuboCop::RakeTask.new
-end