epyc: move to Nix 2.18, remove discard references exp feature

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

modules/nix-daemon.nix

@@ -51,6 +51,7 @@ in
       gc.randomizedDelaySec = "1800";
 
       # Inchallah, it works.
+      package = pkgs.nixVersions.nix_2_18;
       # package = lib.mkForce inputs.nixpkgs-unstable.legacyPackages.x86_64-linux.nixVersions.nix_2_17;
 
       # should be enough?
@@ -78,7 +79,6 @@ in
           "auto-allocate-uids"
           # "ca-derivations" this feature is really extremely broken.
           "cgroups"
-          "discard-references"
           "fetch-closure"
           "impure-derivations"
         ];