Verify foreign keys for fixtures

It doesn't really affect us because we don't use fixtures, so we're just
using the new default value.

config/initializers/new_framework_defaults_7_0.rb

@@ -53,7 +53,7 @@ Rails.application.config.active_storage.video_preview_arguments =
 Rails.application.config.active_record.automatic_scope_inversing = true
 
 # Raise when running tests if fixtures contained foreign key violations
-# Rails.application.config.active_record.verify_foreign_keys_for_fixtures = true
+Rails.application.config.active_record.verify_foreign_keys_for_fixtures = true
 
 # Disable partial inserts.
 # This default means that all columns will be referenced in INSERT queries