Long story short you have to deactivate your machine or remove the license from the activation. When you send a request to the mirror it sends a bunch of data inclucing your machine details, all the modules installed, versions, and of course your system ID. In the response from the mirror they have a section with expired that is parsed. So there is nothing server side while on the official mirrors you can do to get rid of this. Maybe submit a patch that adds an advanced setting to hide it.