Unset the priorities for car profiles on unpair.

When the device is unpaired the priorities should not be retained since
on the next pairing we will persist priorities if they are anything
other than UNDEFINED.

Bug: b/31021525

Change-Id: Ifd7dbf93aff3abcd0f6207395fbac90480624415
(cherry picked from commit 5312f3c9017634ed596a941fc375a6f70ed3aa13)