vmagent: dont update via nixpkgs-update

pkgs/by-name/vm/vmagent/package.nix

@@ -1,4 +1,8 @@
 { lib, victoriametrics }:
+
+# This package is build out of the victoriametrics package.
+# so no separat update prs are needed for vmagent
+# nixpkgs-update: no auto update
 lib.addMetaAttrs { mainProgram = "vmagent"; } (
   victoriametrics.override {
     withServer = false;