Downgrade rubocop 0.48.1 => 0.46.0 (#2628)

* downgrade rubocop 0.48.1 => 0.46.0

* exclude vendor/**/* from rubocop target files

* add frozen_string_literal comment line

* fix percent literal delimited by ( and )

* fix alignment

* remove comment disabling unknown cop

lib/tasks/mastodon.rake

@@ -61,7 +61,6 @@ namespace :mastodon do
     desc 'Set unknown attachment type for remote-only attachments'
     task set_unknown: :environment do
       Rails.logger.debug 'Setting unknown attachment type for remote-only attachments...'
-      # rubocop:disable Rails/SkipsModelValidations
       MediaAttachment.where(file_file_name: nil).where.not(type: :unknown).in_batches.update_all(type: :unknown)
       Rails.logger.debug 'Done!'
     end