Are you sure? I just checked my device, and while all notifications are toggled under a catch-all "notifications" category, I am able to customize this from within the app, and shipment notifications are their own category.
They certainly don’t want you to disable deal notifications and make it very difficult to do so.
It’s like the old quote about fire extinguishers: if you don’t know where one is, it doesn’t exist. If a reasonable effort cannot find the setting, it doesn’t exist.