Check Module#ruby2_keywords arity

It is considered a mistake, because calling this method with no
arguments has no effect.

Author: nobu

lib/ruby2_keywords.rb

@@ -1,15 +1,15 @@
 class Module
   unless respond_to?(:ruby2_keywords, true)
     private
-    def ruby2_keywords(*)
+    def ruby2_keywords(name, *)
       # nil
     end
   end
 end
 
 main = TOPLEVEL_BINDING.receiver
 unless main.respond_to?(:ruby2_keywords, true)
-  def main.ruby2_keywords(*)
+  def main.ruby2_keywords(name, *)
     # nil
   end
 end