Fix timing issues on convertion migration award emoji
What does this MR do?
Fixes timing issues while migrating the data from the
notes table to the
award_emoji table. Also, it adds a down migration for some of the data.
Are there points in the code the reviewer needs to double check?
I've tested the queries myself on PG only, as at of this time I haven't got MySQL yet. Though there shouldn't be a problem here.
What are the relevant issue numbers?
Closes #18385 (closed)