It was missing for me, but I got it back.
I did the following:
1. Turned bluetooth on on my phone and laptop
2. Ran the iPhone Mirroring app on my laptop
3. Went through the steps to get that working, including clicking "allow" for phone notifications to pass through
The option is now showing correctly in settings / notifications.
I've since turned Bluetooth back off, and the option has remained. I've not had a notification yet to check it actually works, but it seems ok.