To the best of my knowledge, at the moment it is not possible to retract a delete vote:
* The feature request Ability to retract reopen/delete votes on Meta Stack Exchange is not marked status-completed.
* Other questions on Meta Stack Exchange about this problem seem to be often closed as duplicate of this post. Among the linked questions I can see this question from January 2017: Why can't I undo a delete vote?
* The answer to Is it possible to withdraw a deletion vote? on Mathematics Meta says the same thing. (It is a post from 2015, but I have not seen some update about this on that meta site since then.)