Remove unused accessors left and right on DeleteStatement

Use `relation` and `wheres` instead.

activerecord/lib/arel/nodes/delete_statement.rb

@@ -3,17 +3,12 @@
 module Arel # :nodoc: all
   module Nodes
     class DeleteStatement < Arel::Nodes::Node
-      attr_accessor :left, :right, :orders, :limit, :offset, :key
-
-      alias :relation :left
-      alias :relation= :left=
-      alias :wheres :right
-      alias :wheres= :right=
+      attr_accessor :relation, :wheres, :orders, :limit, :offset, :key
 
       def initialize(relation = nil, wheres = [])
         super()
-        @left = relation
-        @right = wheres
+        @relation = relation
+        @wheres = wheres
         @orders = []
         @limit = nil
         @offset = nil
@@ -22,18 +17,18 @@ def initialize(relation = nil, wheres = [])
 
       def initialize_copy(other)
         super
-        @left  = @left.clone if @left
-        @right = @right.clone if @right
+        @relation = @relation.clone if @relation
+        @wheres = @wheres.clone if @wheres
       end
 
       def hash
-        [self.class, @left, @right, @orders, @limit, @offset, @key].hash
+        [self.class, @relation, @wheres, @orders, @limit, @offset, @key].hash
       end
 
       def eql?(other)
         self.class == other.class &&
-          self.left == other.left &&
-          self.right == other.right &&
+          self.relation == other.relation &&
+          self.wheres == other.wheres &&
           self.orders == other.orders &&
           self.limit == other.limit &&
           self.offset == other.offset &&