get rid of old worker

app/workers/project_import_worker.rb

-class ProjectImportWorker
-  include Sidekiq::Worker
-
-  # TODO: enabled retry - disabled for QA purposes
-  sidekiq_options queue: :gitlab_shell, retry: false
-
-  def perform(current_user_id, tmp_file, namespace_id, path)
-    current_user = User.find(current_user_id)
-
-    project = Gitlab::ImportExport::Importer.execute(archive_file: tmp_file,
-                                                     owner: current_user,
-                                                     namespace_id: namespace_id,
-                                                     project_path: path)
-    if project
-      project.repository.after_import
-    else
-      logger.error("There was an error during the import: #{tmp_file}")
-    end
-  end
-
-  def logger
-    Sidekiq.logger
-  end
-end