ERP5Type: don't publish workflow methods
Wrapping a method in a workflow method should not change the publishable state the method. If the original method is not publishable, wrapping it in a workflow method should not make it publishable. If the original method is publishable, then the wrapped method should still be publishable. This was always intended to work like this, as we can see in the code comment in `WorkflowMethod.__init__` but was not properly tested and got broken at some point. It's important to restore the behavior, because workflow methods such as `validate` should not be published, users must only be able to use the user interface transitions freely, workflow methods transitions are only available if developer expose them in a script - and perform the necessary consistency and security checks in that script.