network: adds missing strv_free()

Fixes oss-fuzz#11285.

src/network/networkd-network.c

@@ -369,6 +369,7 @@ void network_free(Network *network) {
         strv_free(network->search_domains);
         strv_free(network->route_domains);
         strv_free(network->bind_carrier);
+        strv_free(network->router_search_domains);
 
         netdev_unref(network->bridge);
         netdev_unref(network->bond);