Here’s the link to the ota.zip if you need it 
(to be clear I wouldn’t suggest using it if you didn’t get an update notification, there might be a reason for it)
You don’t need to patch a new boot image, the usual re-root instructions for OTA updates are a lot less hassle. Just don’t reboot after the update and install Magisk to the other slot, didn’t have issues this time around either, everything worked fine.