You don't know why he or she downvoted. It could be for that reason, or any other. It's likely the user doesn't know you fixed it. If someone left a comment, you can @-reply that commenter saying you fixed it. That might prompt them to look at your post and that might lead them to remove the downvote. But you don't even know (you can't know, you can only surmise or guess or believe) that the commenter is the downvoter. I quite often read an answer that I think is wrong but has a zero score, see a comment pointing out the error, and then downvote the post. And I usually don't come back later to see if the error was fixed. If that's what happened on your post, you should just accept the downvote as the cost of typing a little too quickly.
There was a feature request to notify downvoters when posts were edited; it was declined. You can vote for it if you think that might help.
Should is a loaded word. Ideally yes, if you use downvotes to say you think something is wrong, you should remove them once it's right. But the downvoter may not know you fixed it, or they may object to something else.