I have found this link ! It say ok! Allow to enable or disable default application in developer portal
But i dont't found tenant-conf.json!
In this link ,Customize per tenantit say this file is located in / _system/config/apimgt/applicationdata/tenant-conf.json
From API Manager 4.2.0 onwards the tenant-conf.json configurations were moved to the Admin portal. Please find the details here and here.