The answer is to comment out or delete everything from line 51 to 86 in the file admin/tool/policy/templates/guestconsent.moustache. Or just delete everything in the whole file and leave it empty. But do not delete the file itself.
This will allow you to still set a policy to All users or Guest users but avoid the cookie popup.
There are many much better cookie consent tools out there that handle consents properly for different types of cookies. Disabling this will allow you to use those instead.