I bought a second license on my account, but it turns out the person I bought that second license for no longer has a use for it, and in fact even sold their Mac. Is there any way I can drop one of the licenses from my two license account so I can renew it with just one license?
Yes, under the same subscription. I added one of the licenses to the subscription last November, which cost equivalent to buying that one license for the remainder of the subscription period.