You can just unplug this from the speaker in the footwell.
IIRC...If you drop the trim panel, you'll see the speaker and it has 1 big white plug, 1 small white plug, and 1 small black plug. One of these is for that annoying "PONG PONG PONG" sound for the sensor.
I know this because mine was disconnected since owning the car and I got curious. Immediately disconnected it soon after
Pretty sure the gong does the warning chimes as well, you could disconnect the module behind the right hand side trim in the boot if you want to keep the gong.