Here's how I'd approach it: "Hon, we have all these bottles in here. I don't want them, and apparently you no longer have any use for them, either. I'd like to have this space back. Is there any reason I can't get rid of them?"
See what he says. If he claims you might have a party or guests that want to drink, then just tell him you have no problem with picking up stuff for guests in that event, but you don't see the point of keeping it around. It's been six months. If he's not shown any signs of continuing to drink he shouldn't have a problem getting rid of it.