[ruby/set] The arity of initialize_clone is -1 in Ruby >= 3

https://github.com/ruby/set/commit/32a9689696

lib/set.rb

@@ -286,19 +286,11 @@ class Set
     @hash = orig.instance_variable_get(:@hash).dup
   end
 
-  if Kernel.instance_method(:initialize_clone).arity != 1
   # Clone internal hash.
   def initialize_clone(orig, **options)
     super
     @hash = orig.instance_variable_get(:@hash).clone(**options)
   end
-  else
-    # Clone internal hash.
-    def initialize_clone(orig)
-      super
-      @hash = orig.instance_variable_get(:@hash).clone
-    end
-  end
 
   def freeze    # :nodoc:
     @hash.freeze