Merge pull request #19983 from kamipo/remove_unused_require

Remove unused require

activerecord/test/cases/adapters/mysql/case_sensitivity_test.rb

 require "cases/helper"
-require 'models/person'
 
 class MysqlCaseSensitivityTest < ActiveRecord::TestCase
   class CollationTest < ActiveRecord::Base

activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb

 require "cases/helper"
-require 'models/person'
 
 class Mysql2CaseSensitivityTest < ActiveRecord::TestCase
   class CollationTest < ActiveRecord::Base