presets(nginx): actually enable the prometheus exporter

Changed files
+1
global
gensokyo
presets
+1
global/gensokyo/presets/nginx.nix
···
}
(lib.mkIf presetConf.vmetrics {
+
services.prometheus.exporters.nginx.enable = true;
services.vmagent.prometheusConfig.scrape_configs = [
{
job_name = "nginx";