Revert "[ALLI-2538] Changed scheduled alerts to use first_indexed field like other "new items" functionality does."

This reverts commit eee0816346f788b02f3dbe144b37aefdb2f11010.
Revert "[ALLI-2296] Fixed scheduled alerts to switch configurations properly."

This reverts commit 8b81925304e6b337a388753d55a7038dc88e9f93.