It can’t. You are on the dev release channel, and this is an upgrade from Android 12 (S) to Android 13 (T).
There is no OTA upgrade yet, this will have to be specially prepared by the developers (current status for FP3: to be planned). And even when it might arrive, OTA upgrades are only made available on the stable release channel, not on dev (also see given link before).
You will have to upgrade manually.
It is, unofficially. Several users have successfully done so, but for this you need an install file which can be installed via ADB sideload (which is not the file format on the image download pages, because the official way to install on the Fairphone 3/3+ is different as per official install instructions), see here …