Revert "add is_keynote attribute to event_types"

This reverts commit 96253b1fe048e2052fc35e961c5afbf27d0ef740.

Conflicts:
	app/models/conference.rb

app/controllers/admin/event_types_controller.rb

@@ -49,10 +49,7 @@ module Admin
     private
 
     def event_type_params
-      params.require(:event_type).permit(:title, :length,
-                                         :minimum_abstract_length,
-                                         :maximum_abstract_length,
-                                         :color, :is_keynote)
+      params[:event_type]
     end
   end
 end