remove the mounted? method

we know the routes should not be "optimized" when mounting an
application

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -621,7 +621,7 @@ module ActionDispatch
             _routes = @set
             app.routes.define_mounted_helper(name)
             app.routes.extend Module.new {
-              def mounted?; true; end
+              def optimize_routes_generation?; false; end
               define_method :find_script_name do |options|
                 super(options) || begin
                 prefix_options = options.slice(*_route.segment_keys)

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -641,12 +641,8 @@ module ActionDispatch
                           :trailing_slash, :anchor, :params, :only_path, :script_name,
                           :original_script_name]
 
-      def mounted?
-        false
-      end
-
       def optimize_routes_generation?
-        !mounted? && default_url_options.empty?
+        default_url_options.empty?
       end
 
       def find_script_name(options)