Well ideally your mech would have enough cage length to take up the slack when you're in the little ring, but as you shouldn't be riding smallest-smallest like in that pic anyway, it'd just leave it if the tension's good in the big ring (and if that's what you'll ride in most). If you're really worried about it though, you might be able to take a few links out and still have the chain acceptably tight - you just have to make sure your chain still runs through the mech in an s-bend in big-big.
Well ideally your mech would have enough cage length to take up the slack when you're in the little ring, but as you shouldn't be riding smallest-smallest like in that pic anyway, it'd just leave it if the tension's good in the big ring (and if that's what you'll ride in most). If you're really worried about it though, you might be able to take a few links out and still have the chain acceptably tight - you just have to make sure your chain still runs through the mech in an s-bend in big-big.