Optimise query to populate notification statuses
Optimise query to populate notification statuses

Investigation with EXPLAIN and EXPLAIN ANALYZE for the notification
history table shows this is another instance of [1] but for the key
type column. Swapping "!=" for "IN" solves the problem.

[1]: https://github.com/alphagov/notifications-api/pull/3360

alphagov/notifications-api,alphagov/notifications-api