fix: Future truncated shards return duplicate results

[devanbenz]

This PR resolves an issue where we are seeing the following

- Create a database with a shard group duration of 72 hours.
- Insert a data point in the future.
- Run truncate-shards.
- Insert the same datapoint again into the future.
- Query for that time range. Two data points will return.
- Inspect the shards, each datapoint is in a different shard.Closes #

Currently a WIP