Replace default RDNS value in description

Author: bbiggerr

openapi.yaml

@@ -10117,7 +10117,7 @@ paths:
       description: >
         Sets RDNS on an IP Address. Forward DNS must already be set up for
         reverse DNS to be applied. If you set the RDNS to `null` for public
-        IPv4 addresses, it will be reset to the default _members.linode.com_
+        IPv4 addresses, it will be reset to the default _ip.linodeusercontent.com_
         RDNS value.
       operationId: updateIP
       x-linode-cli-action: ip-update