Remove unused sidekiq worker

app/workers/repository_archive_worker.rb

-class RepositoryArchiveWorker
-  include Sidekiq::Worker
-
-  sidekiq_options queue: :archive_repo
-
-  attr_accessor :project, :ref, :format
-
-  def perform(project_id, ref, format)
-    @project = Project.find(project_id)
-    @ref, @format = ref, format.downcase
-
-    repository = project.repository
-
-    repository.clean_old_archives
-
-    return unless file_path
-    return if archived? || archiving?
-
-    repository.archive_repo(ref, storage_path, format)
-  end
-
-  private
-
-  def storage_path
-    Gitlab.config.gitlab.repository_downloads_path
-  end
-
-  def file_path
-    @file_path ||= project.repository.archive_file_path(ref, storage_path, format)
-  end
-
-  def pid_file_path
-    @pid_file_path ||= project.repository.archive_pid_file_path(ref, storage_path, format)
-  end
-
-  def archived?
-    File.exist?(file_path)
-  end
-
-  def archiving?
-    File.exist?(pid_file_path)
-  end
-end