The JobStatistics table is going to be deleted. There are currently
3 tasks which use the JobStatistics model via the Statistics DAO, so we
need to make sure that these tasks aren't being used before they are
deleted in a separate PR.
This commit deletes:
* The `create_initial_notification_statistic_tasks` function which gets
used to call the `record_initial_job_statistics` task.
* The `create_outcome_notification_statistic_tasks` function which gets
used to call the `record_outcome_job_statistics` task.
* And the scheduling of the `timeout-job-statistics` scheduled task.