Make `marshal_load` public

Ruby specs expected this method to be public

lib/ostruct.rb

@@ -203,6 +203,7 @@ class OpenStruct
   # Provides marshalling support for use by the Marshal library.
   #
   alias_method :marshal_load, :update_to_values! # :nodoc:
+  public :marshal_load
 
   #
   # Used internally to defined properties on the