I don't think the vote-lock should be removed for answers when the question is edited.
My argument is that no edit to any question should ever change your view on an answer.
There are two situations where this proposal could be applied:
Users answering unclear questions, providing nothing more but guesses. Asker adds more info --> Answer seems better now
The tooltip on the upvote answer button says
This answer is useful
This answer looks useful
If you intend to try out an answer, try it out first and then upvote it. Or downvote it and/or leave a comment if it doesn't work. If you can improve the answer, you can (suggest an) edit; an edit allows you to retract votes. (But note ...
We had people messing around voting up and down the same question repeatedly in an attempt presumably to get the attention of the answerer for some issue or other. Rather than allow people to basically interrupt a poster by waving in their face all day we restrict changing voting except within an initial grace period or if the post is edited.
Feel free to ...