prometheus-node-exporter-lua: fix nat scraper

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua

@@ -266,8 +266,7 @@ end
 function scraper_nat()
   -- documetation about nf_conntrack:
   -- https://www.frozentux.net/iptables-tutorial/chunkyhtml/x1309.html
-  -- local natstat = line_split(get_contents("/proc/net/nf_conntrack"))
-  local natstat = line_split(get_contents("nf_conntrack"))
+  local natstat = line_split(get_contents("/proc/net/nf_conntrack"))
 
   nat_metric =  metric("node_nat_traffic", "gauge" )
   for i, e in ipairs(natstat) do