Monitoring: Enable textfile collector

nixos/modules/monitoring/exporters/node.nix

@@ -35,8 +35,8 @@ in {
       #"softnet" # not in nixpkgs 19.09
       "stat"
       "systemd"
-      # "textfile"
-      # "textfile.directory /run/prometheus-node-exporter"
+      "textfile"
+      "textfile.directory /run/prometheus-node-exporter"
       #"thermal_zone" # not in nixpkgs 19.09
       "time"
       #"udp_queues" # not in nixpkgs 19.09