Drop remains of resetting subscriptions to default

This got added in #4186 and #4384 and then removed while switching interfaces
to bootstrap in #8341.

Fixes #16198 which was caused by a spammer script going back and forth on
routes with format=js because it could not acknowledge a status message
anymore. Thanks spammer, keep up the good work!

src/api/app/controllers/webui/users/subscriptions_controller.rb

@@ -7,11 +7,6 @@ class Webui::Users::SubscriptionsController < Webui::WebuiController
   def index
     @user = User.session!
     @groups_users = @user.groups_users.includes(:group).order('groups.title')
-
-    respond_to do |format|
-      format.html
-      format.js
-    end
   end
 
   def update