[border-agent] update logging for filtered messages (#8045)
[border-agent] update logging for filtered messages (#8045)

Update border agent logging for filtered messages to debug level to
avoid confusion, because it's actually not a error case.
srickardti/openthread,jwhui/openthread,openthread/openthread,srickardti/openthread,srickardti/openthread,openthread/openthread,openthread/openthread,jwhui/openthread,openthread/openthread,jwhui/openthread,srickardti/openthread,jwhui/openthread