Do you mean you want to remove the box and leave the wiring in the wall? I believe it’s code in most places that you have to make wire splices like that accessible and not just shoved into the wall. So, in your case, code would require you to leave it as-is, with the wires capped behind a blank cover plate.

Plus, that junction box is likely nailed into the stud in the wall. You’d have to pry it out, which probably means wrecking then patching the drywall around it. Cap the wires, put on a blank cover, and call it a day.