you need to re roll your operations until you get that challenge in there then you will be able to unlock the patch
You don't necessarily need to reroll the operations. Just press A on the game mode operations and see if it's there to be selected. Each operation has 10 challenges to choose from that can be swapped out whenever you feel like it. These change automatically every 14 days or so or you can just reroll that operation if there's none there that interest you.
I've got this one active right now but it just doesn't seem to want to unlock. Three games in a row I've gotten kills with less than 5 seconds to go and still hasn't unlocked. The last one was with less than a second to go.