Move push priority concerns from Event and Mention into Native push target

app/models/event.rb

@@ -37,10 +37,6 @@ class Event < ApplicationRecord
     Event::Description.new(self, user)
   end
 
-  def high_priority_push?
-    action.card_assigned?
-  end
-
   private
     def dispatch_webhooks
       Event::WebhookDispatchJob.perform_later(self)

app/models/mention.rb

@@ -18,10 +18,6 @@ class Mention < ApplicationRecord
     source
   end
 
-  def high_priority_push?
-    true
-  end
-
   private
     def watch_source_by_mentionee
       source.watch_by(mentionee)