Drop unused rubocop tasks

lib/tasks/rubocop.rake

@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-unless Rails.env.production?
-  require 'rubocop/rake_task'
-
-  RuboCop::RakeTask.new(:rubocop) do |task|
-    task.patterns = []
-    task.options = ['--display-cop-names']
-  end
-
-  namespace :rubocop do
-    desc 'Generate .rubocop_todo.yml'
-    task :auto_gen_config do
-      sh 'rubocop --display-cop-names --auto-gen-config --auto-gen-only-exclude'
-    end
-  end
-end