Instinct notifications for Snapchat and Facebook Messenger

Over the last few weeks my phone has been giving me notifications for Facebook Messenger and Snapchat that they are "Updating Messages".

It's usually such a quick notification that it goes away before I look at my watch. However it's driving me crazy because it's not an actual notification.

Does anyone know how to stop these apps from giving me these notifications? I've checked both apps and I've found nothing in the notification settings.