[Refactor] Update replications page to use `self_service` struct

[jcace]

• The API response from /replications API has been restructured, so now the is_self_service variable is under an object called self_service, like so:

            "self_service": {
                "is_self_service": true,
                "last_update": "0001-01-01T00:00:00Z",
                "status": "",
                "message": ""
            }

So the column Self Service needs to come from replication.self_service.is_self_service now instead of just replication.is_self_service

This change was introduced in the Replications Schema Updates on DDM (ref: https://github.com/application-research/delta-dm/commit/692c54d40a3bb62a1bd21ebab8e8699a85a43bea)