Remove newly-redundant OrderedSet

lib/active_model/ordered_set.rb

@@ -1,25 +0,0 @@
-module ActiveModel
-  class OrderedSet
-    def initialize(array)
-      @array = array
-      @hash = {}
-
-      array.each do |item|
-        @hash[item] = true
-      end
-    end
-
-    def merge!(other)
-      other.each do |item|
-        next if @hash.key?(item)
-
-        @hash[item] = true
-        @array.push item
-      end
-    end
-
-    def to_a
-      @array
-    end
-  end
-end

lib/active_model/serializer.rb

@@ -1,6 +1,5 @@
 require "active_support/core_ext/class/attribute"
 require "active_support/core_ext/module/anonymous"
-require "set"
 
 module ActiveModel
   # Active Model Serializer