A seller can cancel any individual bidder's bids (one cancellation removes them all) up until the auction ends (it is cancelling them all AND ending early without a winner that is not allowed in the last 12 hours). But you are not under any obligation to do so nor to make yourself available to do so.
I suggest you wait to see what the winner does now: request an order cancellation or pay or do nothing. If s/he requests an order cancellation accept it and get on with relisting or making a Second Chance Offer. If s/he pays, ship. If s/he doesn't do anything cancel after 4 days for non-payment.
Many would cancel now "at buyer's request" interpreting the request to cancel the bid as including a request to cancel the order if s/he wins, but I'd wait and see.
Also add the bidder to your Block Bidder/Buyer List.
