Add comment to make sure both out of stock modal get updated.

There is no easy way to share template between AngularJS and Rails. The
modal in `edit.html.haml` is a copy of app/assets/javascripts/templates/out_of_stock.html.haml,
so we need to update both if either of them is updated.

app/assets/javascripts/templates/out_of_stock.html.haml

@@ -1,3 +1,4 @@
+// please update the modal html in app/view/checkout/edit.html.haml if updating this template
 %a.close-reveal-modal{"ng-click" => "$close()"}
   %i.ofn-i_009-close
 

app/views/checkout/edit.html.haml

@@ -20,9 +20,9 @@
     = render partial: "shopping_shared/order_cycles"
 
   %div{ "data-controller": "guest-checkout", "data-guest-checkout-distributor-value": @order.distributor.id }
-    = #TODO create new component ? reuse out_of_stock.html.haml template
     - if @any_out_of_stock
       = render ModalComponent.new(id: "out-of-stock-items", modal_class: "medium" ,instant: true, close_button: false) do
+        - # please update app/assets/javascripts/templates/out_of_stock.html.haml if updating the modal html
         %a.close-reveal-modal{"data-action": "click->modal#close" }
           %i.ofn-i_009-close
         %h3