It's very simple to retract a close vote (although doing so means you can't vote again on that post) but unless I'm missing something it's not possible to retract a re-open vote. Mistakes occur regardless of how hard we try to avoid them. In most cases these can easily be self-corrected wither via edit or retraction. I'd like to see the capability to retract a re-open vote like we have for close votes. I've reviewed Add the ability to retract reopen and delete votes on meta which covers this exactly and I've had some conversation in comments with @animuson regarding concerns/limitations. I hope that if you are reading this question that you'll take the time to visit Add the ability to retract reopen and delete votes and upvote both the Q and the A in the hope that we can get some traction on this.
Further research driven by the answers received thus far indicate that this feature has seen some interest over the years and I'm not the first to suggest it. this related bug report was closed as status-by design, which to me means this is not a bug, hence the feature request.