The sequence of events:
- I flagged an answer as "not an answer"
- I downvoted the answer
- The user responded to the downvote by deleting the answer
- As of this writing, the flag still appears in my flagging summary
- What will happen now? Will the flag be left alone and just sit there "waiting for review"?
- What should happen? There probably isn't much of a need for a moderator review if the post was self-deleted.