tests: replace workoff_active_jobs with perform_enqueued_jobs.

test/test_helper.rb

@@ -51,15 +51,6 @@ module TestHelpers
       Thread.current[:pixiv_comic_session_cache_key] = Cache.get(PixivWebAgent::COMIC_SESSION_CACHE_KEY)
     end
   end
-
-  # XXX replace with `perform_enqueued_jobs` after rails 6 upgrade.
-  def workoff_active_jobs
-    queue_adapter.enqueued_jobs.each do |job_data|
-      args = ActiveJob::Arguments.deserialize(job_data[:args])
-      job = job_data[:job].new(*args)
-      job.perform_now
-    end
-  end
 end
 
 class ActiveSupport::TestCase