Use parent strategy for associations in factories

See https://github.com/thoughtbot/factory_bot/blob/master/GETTING_STARTED.md#build-strategies-1

spec/support/factory_bot.rb

@@ -3,7 +3,3 @@
 FactoryBot::SyntaxRunner.class_eval do
   include RSpec::Mocks::ExampleMethods
 end
-
-# Use FactoryBot 4.x behavior:
-# https://github.com/thoughtbot/factory_bot/blob/master/GETTING_STARTED.md#associations
-FactoryBot.use_parent_strategy = false