I am getting an explant in 2 weeks. Should I stop doing weights for upper body now? Or it doesn’t matter?

No, keep on exercising until the day of surgery. You will be restricted for a while after surgery to allow yourself to hesl.

It should not matter if you continue to do weights between now and your surgery. I don't recommend any new lifting programs where you might injury the muscle, but keeping healthy with your current routine should be fine.