Common/nix: remove unneeded nixpath workaround, update comment

roles/common/programs/nix.nix

@@ -58,9 +58,10 @@
       };
       # Write the system's nixpkgs into the registry to avoid mixing nixpkgs versions
       # https://dataswamp.org/~solene/2022-07-20-nixos-flakes-command-sync-with-system.html
+
+      # Since 24.05 this is already done for nixpkgs, but it doesn't keep the patches
+      # so I'm keeping this around just in case
       system.flake = systemPkgs;
     };
-    # I removed this in the past since I thought that I didn't need it, but turns out comma does :)
-    nixPath = ["nixpkgs=${systemPkgs}"];
   };
 }