reltags: remove mark inactive button from artist urls.

In related tags, remove the (X) button next to artist urls for marking
them as inactive. This was broken because it didn't record the change
to the is_active flag in the artist history.

config/routes.rb

@@ -63,7 +63,7 @@ Rails.application.routes.draw do
       get :banned
     end
   end
-  resources :artist_urls, only: [:index, :update]
+  resources :artist_urls, only: [:index]
   resources :artist_versions, :only => [:index, :show] do
     collection do
       get :search