Remove #one method

It hasn't been used since cdce4a5.

Author: bquorning

lib/rubocop-rspec.rb

@@ -11,7 +11,6 @@
 require_relative 'rubocop/rspec/node'
 require_relative 'rubocop/rspec/top_level_describe'
 require_relative 'rubocop/rspec/wording'
-require_relative 'rubocop/rspec/util'
 require_relative 'rubocop/rspec/language'
 require_relative 'rubocop/rspec/language/node_pattern'
 require_relative 'rubocop/rspec/concept'

lib/rubocop/cop/rspec/describe_method.rb

@@ -18,7 +18,6 @@ module RSpec
       #   end
       class DescribeMethod < Cop
         include RuboCop::RSpec::TopLevelDescribe
-        include RuboCop::RSpec::Util
 
         MSG = 'The second argument to describe should be the method '\
               "being tested. '#instance' or '.class'."