srv.vmagent: fix outdated remoteWriteUrl

Changed files
+1
systems
koumakan
services
+1
systems/koumakan/services/telemetry/victoriametrics.nix
···
services.vmagent = {
enable = true;
+
remoteWriteUrl = "http://${config.services.victoriametrics.listenAddress}/api/v1/write";
prometheusConfig = {
global = {
scrape_interval = "1m";