They probably buried it for a reason, so you wouldn't do that.
Doesn't this chime go off after a short time? One thing you could do is buckle up before you turn on the ignition.
Also you might check your fuse box and see what fuse controls this alarm. Possibly you could pull that fuse and not affect other items. Depends what else is on that fuse.
Otherwise, I guess you'll have to slip the radio out to do this, or pay an audio shop to do it for you.