Remove parent transaction state

As far as I can tell nobody is setting this variable.

activerecord/lib/active_record/connection_adapters/abstract/transaction.rb

 module ActiveRecord
   module ConnectionAdapters
     class TransactionState
-      attr_reader :parent
-
       VALID_STATES = Set.new([:committed, :rolledback, nil])
 
       def initialize(state = nil)
         @state = state
-        @parent = nil
       end
 
       def finalized?

activerecord/lib/active_record/core.rb

@@ -521,10 +521,6 @@ def update_attributes_from_transaction_state(transaction_state, depth)
           clear_transaction_record_state
           @reflects_state[depth] = true
         end
-
-        if transaction_state.parent
-          update_attributes_from_transaction_state(transaction_state.parent, depth+1)
-        end
       end
     end