Since ddclient@24ba945 (v3.10.0), the type and meaning of the "ipv6"
option has changed. This resulted in the following warning when
starting the service:
WARNING: file /run/ddclient/ddclient.conf, line 13:
Invalid Value for keyword 'ipv6' = 'no'
This therefore removes the matching boolean option.
More advanced configurations can use the "extraConfig" option instead.