this was a typo introduced in #10282. We don't want to end up doing the
`replace_stream_ordering_column` update after anything that comes up in
migration 60/03.
* Move background update names out to a separate class
`EventsBackgroundUpdatesStore` gets inherited and we don't really want to
further pollute the namespace.
* Migrate stream_ordering to a bigint
* changelog
Richard van der Hoff