Also it's gone completely from the GUI as of V10.4.0
Jamf Distribution Server (JDS)—Starting with Jamf Pro 10.4.0, Jamf Distribution Server (JDS) settings are no longer directly accessible via the Jamf Pro user interface. JDS functionality will be completely removed in a future release of Jamf Pro. Important: If you are still using the JDS, you should not upgrade to Jamf Pro 10.4.0. Jamf discontinued the JDS at the end of 2017. We do not recommend using JDS in its current state, as we cannot guarantee it will continue to function as expected. For questions or assistance in migrating away from the JDS, contact your Jamf account representative.
And they've updated most (all?) KB articles about JDS to add the line
Disclaimer: This article is no longer being updated. The Jamf Distribution Server was discontinued at the end of 2017.
I think it'd be a good idea to get yourself off it sooner rather than later.