As stated earlier, the link in your error message is not working. Click on it and you can see for yourself.
You need to either find a new mirror for qemu-firmware-jenkins that isn’t kraxel.org, or disable the repository for qemu-firmware-jenkins. Then your update should work.
Incidentally, kraxel.org was down completely the last time I clicked on it the other day. It is now back up but the repos link is missing.