Add preference setting for delete toot modal (#3368)

* Set delete_modal preference to true by default
* Does not show confirmation modal if delete_modal is false
* Add ja translation for preference setting page

app/controllers/settings/preferences_controller.rb

@@ -35,6 +35,7 @@ class Settings::PreferencesController < ApplicationController
     params.require(:user).permit(
       :setting_default_privacy,
       :setting_boost_modal,
+      :setting_delete_modal,
       :setting_auto_play_gif,
       notification_emails: %i(follow follow_request reblog favourite mention digest),
       interactions: %i(must_be_follower must_be_following)