tests, remove unneeded requires.

activerecord/test/cases/adapters/postgresql/enum_test.rb

 # -*- coding: utf-8 -*-
 require "cases/helper"
 require 'support/connection_helper'
-require 'active_record/base'
-require 'active_record/connection_adapters/postgresql_adapter'
 
 class PostgresqlEnumTest < ActiveRecord::TestCase
   include ConnectionHelper

activerecord/test/cases/adapters/postgresql/hstore_test.rb

 # encoding: utf-8
-
 require "cases/helper"
-require 'active_record/base'
-require 'active_record/connection_adapters/postgresql_adapter'
 
 class PostgresqlHstoreTest < ActiveRecord::TestCase
   class Hstore < ActiveRecord::Base

activerecord/test/cases/adapters/postgresql/json_test.rb

 # encoding: utf-8
-
 require "cases/helper"
-require 'active_record/base'
-require 'active_record/connection_adapters/postgresql_adapter'
 require 'support/schema_dumping_helper'
 
 module PostgresqlJSONSharedTestCases

activerecord/test/cases/adapters/postgresql/uuid_test.rb

 # encoding: utf-8
-
 require "cases/helper"
-require 'active_record/base'
-require 'active_record/connection_adapters/postgresql_adapter'
 require 'support/schema_dumping_helper'
 
 module PostgresqlUUIDHelper