set explicitly the https protocol in the delivery locations url

see: https://api.rubyonrails.org/v7.1.3.4/classes/ActionView/RoutingUrlFor.html

app/views/delivery_locations/index.json.jbuilder

@@ -5,7 +5,7 @@ json.array!(@delivery_locations) do |delivery_location|
   if Rails.env.test?
     json.path delivery_location_path(delivery_location, format: :json)
   else
-    json.url delivery_location_url(delivery_location, format: :json)
+    json.url delivery_location_url(delivery_location, format: :json, protocol: 'https')
   end
   json.partial! 'holding_locations/json_partials/library',
                 library: delivery_location.library