domains_dns_delHost: fix record key in comment

[kurkurzz]

api.domains_dns_delHost('example.com', {
            "RecordType": "A", <-- old
            "HostName": "test", <-- old
            "Type": "A", <-- new
            "Name": "test", <-- new
            "Address": "127.0.0.1"
        })

This is just a simple documentation update. Additional work need to be done to ensure consistent usage of key ("RecordType" or"Type") throughout all the functions.