Use Module#include instead of send :include, since now is a public method [ci skip]

ref https://bugs.ruby-lang.org/issues/8846

activerecord/lib/active_record/fixtures.rb

@@ -132,7 +132,7 @@ class FixtureClassNotFound < ActiveRecord::ActiveRecordError #:nodoc:
   #         Digest::SHA2.hexdigest(File.read(Rails.root.join('test/fixtures', path)))
   #       end
   #     end
-  #     ActiveRecord::FixtureSet.context_class.send :include, FixtureFileHelpers
+  #     ActiveRecord::FixtureSet.context_class.include FixtureFileHelpers
   #
   # - use the helper method in a fixture
   #     photo:
@@ -522,7 +522,7 @@ def self.create_fixtures(fixtures_directory, fixture_set_names, class_names = {}
           update_all_loaded_fixtures fixtures_map
 
           connection.transaction(:requires_new => true) do
-            deleted_tables = Set.new 
+            deleted_tables = Set.new
             fixture_sets.each do |fs|
               conn = fs.model_class.respond_to?(:connection) ? fs.model_class.connection : connection
               table_rows = fs.table_rows

guides/source/upgrading_ruby_on_rails.md

@@ -534,7 +534,7 @@ module FixtureFileHelpers
     Digest::SHA2.hexdigest(File.read(Rails.root.join('test/fixtures', path)))
   end
 end
-ActiveRecord::FixtureSet.context_class.send :include, FixtureFileHelpers
+ActiveRecord::FixtureSet.context_class.include FixtureFileHelpers
 ```
 
 ### I18n enforcing available locales