Remove foreign keys in swagger docs

[dankolbman]

The foreign key relationships currently show up inside of the results object inside of the swagger docs:

{
    "_links": {
        "next": "/genomic-files?after=1519402953",
        "self": "/genomic-files?after=1519402952"
    },
    "_status": {
        "code": 200,
        "message": "success"
    },
    "limit": 10,
    "results": [
        {
            "_links": "string",
            "biospecimen_id": "string",
            "kf_id": "string"
            ...
        }
    ],
    "total": 1

}

However, they show up in the _links section inside of the actual API:

{
    "_links": {
        "next": "/genomic-files?after=1519402953",
        "self": "/genomic-files?after=1519402952"
    },
    "_status": {
        "code": 200,
        "message": "success"
    },
    "limit": 10,
    "results": [
        {
            "_links": {
                "biospecimen": "/biospecimens/BS_00000000"
            },
            "kf_id": "string"
            ...
        }
    ],
    "total": 1

}