If you’re the seller you can remove bids from your own auction.
As a bidder you aren't able to remove your own bids. However, you can request your bid be removed by using the question and answer feature at the bottom of the auction page. If requested within reasonable notice from the close of the auction, the seller is obliged to remove your bid.
This should only happen in urgent situations, so please make sure you’re confident with any bids before placing them.