how to delete elasticsearch cross cluster search seed 5.5.1-1

I'm running elasticsearch 5.5.1-1 and x-pack for monitoring.

Elasticsearch's documentation say's I should be able to add the following code to my elasticsearch.yml file for cross cluster search seeding:

search:
    remote:
        cluster_one: 
            seeds: 1.1.1.1:9300
        cluster_two: 
            seeds: 2.2.2.2:9300

Well that didn't work so I used the API as follows:

PUT _cluster/settings
{
  "persistent": {
    "search": {
      "remote": {
        "cluster_one": {
          "seeds": [
            "1.1.1.1:9300"
          ]
        },
        "cluster_two": {
          "seeds": [
            "2.2.2.2:9300"
          ]
        }
      }
    }
  }
}

That worked fine however I needed to delete cluster_one until it was upgraded to 5.5.1-1 which according to elasticsearch's docs say's should be completed as follows:

PUT _cluster/settings
{
  "persistent": {
    "search": {
      "remote": {
        "cluster_one": {
          "seeds": null 
        }
      }
    }
  }
}

It appears to takeas I get the acknowledgement:

    {
      "acknowledged" : true,
      "persistent" : { },
      "transient" : { }
    }

However if I curl the cluster settings I still see both nodes as follows:

   {
      "persistent" : {
        "search" : {
          "remote" : {
            "cluster_one" : {
              "seeds" : [
                "1.1.1.1:9300"
              ]
            },
            "cluster_two" : {
              "seeds" : [
                "2.2.2.2:9300"
              ]
            }
          }
        }
      },
      "transient" : { }
    }

I wouldn't think I needed to restart elasticsearch after the API call but I tried that to no avail as well.

I also played with quoting/capitalizing null and got this return message which leads me to believe null is a valid value:

{
  "error" : {
    "root_cause" : [
      {
        "type" : "json_parse_exception",
        "reason" : "Unrecognized token 'NULL': was expecting 'null', 'true', 'false' or NaN\n at [Source: org.elasticsearch.transport.netty4.ByteBufStreamInput@6053e99; line: 7, column: 25]"
      }