Do you mean you want to remove the box and leave the wiring in the ceiling? I believe it’s code in most places that you have to make wire splices like that accessible and not just shoved behind drywall. So, in your case, code would require you to leave it as-is, with the wires capped behind a blank cover plate.
If you REALLY want it gone, you could get into the attic and pull the wires back into a junction box mounted to a rafter or joist. Then, patch the ceiling drywall.
Probably easier to just cap the wires and add a blank cover.