When you create a backup (or do a device transfer), we skip messages
with expiration timers. However, we still (unintentionally) include the
reactions for those messages in the backup.
These 'abandoned' reactions were being associated with newly-sent
messages because the new messages had the same ID's as the expiring
messages we skipped in the backup.
It's worth noting that in order to hit this bug, you have to:
- Have messages that are expiring, but have not expired yet
- Those messages have to have reactions
- Those message have to be the most recent messages in your message table
Fixes#11327
