If you don’t plan on using the AC unit anymore, just convert one of the hots into a neutral (mark both ends with white tape) . You’ll need to switch to a single pole breaker though.

Ground wires in Canada are un-insulated, and not rated to carry continuous current. Huge electrical code violation doing this.

Better off just converting one of the hot wires to a neutral (tag the wire with white tape please), and moving the circuit to a single pole breaker.