The act of retracting a flag itself does nothing but remove the flag from the moderator's queue so it doesn't need to be looked at.
If there is a review item currently open for the post, that's a different story. Posts are pushed into that queue for a couple different reasons, and a not an answer flag on the post is one such reason. But the post does have to maintain that reason to stay in the queue. If it no longer matches the criteria for having a review item open for it, then the review task will get invalidated at the next cleanup check the system runs.
So, if your not an answer flag was the only reason that post was in the review queue, then it will get removed from review within about 15 minutes (via invalidating the review task). If there were other flags or other reasons the task was created, nothing will happen.