When a content editor edits a page but does not submit it for review, they get an email notification.
In order to disable the email notifications for a specific state (Draft, Ready For Review and Published), you would need to set the sendNotification column to False in the ContentWorkflowStates table. This can only be done through the database, as there is no option in the UI.
Note: To maintain best practices, make sure to backup your database before doing any change to it.
SET SendNotification = 0
WHERE StateName = 'Desired_State'
AND WorkflowID = (Select WorkflowID
WHERE WorkflowName = 'Content Approval'
AND PortalID = [PORTAL ID GOES HERE])
Once you run this script, you need to clear the cache.
Confirmation: If you load the site again, it won't send notifications, when a content author edits it, anymore.
Content Author: Manuel Gonzalez