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If they are books on your WL then you just need to check mark them and hit unhold. Same if they are on your bookshelf and you want to make them available to wishers.
If you mean you posted the books and they are on WL hold waiting for a response from a wisher-you can't unhold it until it's accepted. Then you can hit Cannot Send to remove it from being posted. If it looks like it's going to time out on the wisher, put your account on vacation and then delete the book from your bookshelf before coming off vacation.