VxAdmin: Show vote for N in manual tally results entry

[arsalansufi]

VxAdmin: We don't say anywhere in the manual tally flow how many seats a contest has, so it can become a guessing game with the "tallies have added up" indicator what number you are trying to get to

Issue automatically created from Slack feedback reported by caroline:
https://votingworks.slack.com/archives/CJU9MSC6S/p1722451411116579?thread_ts=1722451411.116579&cid=CJU9MSC6S