remove unused requires in workers

workers/archive_worker.rb

@@ -1,5 +1,4 @@
 require 'sidekiq/api'
-require 'redis-namespace'
 
 class ArchiveWorker
   include Sidekiq::Worker

workers/screenshot_worker.rb

@@ -1,7 +1,5 @@
 require 'rmagick'
-require 'timeout'
 require 'securerandom'
-require 'thread'
 require 'open3'
 
 class ScreenshotWorker