Revert "Validators should at model level and not at AR:Base level [Closes #4804]"

This reverts commit e11bb95d56.

activerecord/test/cases/validations_test.rb

@@ -9,8 +9,6 @@ require 'models/guid'
 require 'models/owner'
 require 'models/pet'
 require 'models/event'
-require 'models/parrot'
-require 'models/company'
 
 class ProtectedPerson < ActiveRecord::Base
   set_table_name 'people'
@@ -191,12 +189,4 @@ class ValidationsTest < ActiveRecord::TestCase
     end
     assert_equal ["always invalid", "invalid on update"], p.errors[:name]
   end
-
-  def test_validators
-    assert_equal 1, Parrot.validators.size
-    assert_equal 1, Company.validators.size
-    assert_equal 1, Parrot.validators_on(:name).size
-    assert_equal 1, Company.validators_on(:name).size
-  end
-
 end