Document dedupe limit parameter
Created by: MegaphoneJon
https://github.com/civicrm/civicrm-core/pull/11123 https://issues.civicrm.org/jira/browse/CRM-21224
Created by: MegaphoneJon
https://github.com/civicrm/civicrm-core/pull/11123 https://issues.civicrm.org/jira/browse/CRM-21224