Reset column information after schema changed

This fixes the following failures.
https://travis-ci.org/rails/rails/jobs/253990014

Author: y-yagi

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -217,6 +217,8 @@ def test_raises_type_mismatch_with_namespaced_class
       remove_column :admin_users, :region_id if column_exists?(:admin_users, :region_id)
       drop_table :admin_regions, if_exists: true
     end
+
+    Admin::User.reset_column_information
   end
 
   def test_natural_assignment

activerecord/test/cases/null_relation_test.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "cases/helper"
 require "models/developer"
 require "models/comment"