parse: Downgrade NM passthrough warning to debug

With the NetworkManager integration in place there will be many more
cases where "nm-devices" are used, and we don't want to spam system
logs with our warnings.

src/parse.c

@@ -3103,7 +3103,7 @@ handle_network_type(NetplanParser* npp, yaml_node_t* node, const char* key_prefi
             case NETPLAN_DEF_TYPE_WIFI: handlers = wifi_def_handlers; break;
             case NETPLAN_DEF_TYPE_DUMMY: handlers = dummy_def_handlers; break;      /* wokeignore:rule=dummy */
             case NETPLAN_DEF_TYPE_NM:
-                g_warning("netplan: %s: handling NetworkManager passthrough device, settings are not fully supported.", npp->current.netdef->id);
+                g_debug("netplan: %s: handling NetworkManager passthrough device, settings are not fully supported.", npp->current.netdef->id);
                 handlers = ethernet_def_handlers;
                 if (npp->current.netdef->backend != NETPLAN_BACKEND_NM) {
                     g_warning("nm-device: %s: the renderer for nm-devices must be NetworkManager, it will be used instead of the defined one.",