nix-dram: remove nix-dram as default nix binary

nix-dram as default nix binary isn't worth the
maintenance work anymore, CI builds started
failing because of it:
https://ci.b12f.io/pub-solar/os/533/1/2

Automatic builds still happen each night and can be
checked in our fork of nix-dram:
https://github.com/pub-solar/nix-dram/actions

Users of nix-dram can continue to use it via devshells
or nix run github:dramforever/nix-dram -- --version

flake.nix

@@ -42,10 +42,6 @@
       nixos-hardware.url = "github:nixos/nixos-hardware";
 
       nixos-generators.url = "github:nix-community/nixos-generators";
-
-      # PubSolarOS additions
-      nix-dram.url = "github:dramforever/nix-dram";
-      nix-dram.inputs.nixpkgs.follows = "latest";
     };
 
   outputs =
@@ -59,7 +55,6 @@
     , agenix
     , nvfetcher
     , deploy
-    , nix-dram
     , ...
     } @ inputs:
     digga.lib.mkFlake
@@ -120,7 +115,7 @@
             suites = with profiles; rec {
               base = [ core users.pub-solar users.root ];
               iso = base ++ [ base-user graphical pub-solar-iso ];
-              pubsolaros = [ core dram full-install base-user users.root ];
+              pubsolaros = [ core full-install base-user users.root ];
               anonymous = [ pubsolaros users.pub-solar ];
             };
           };

modules/x-os/nix.nix

@@ -18,8 +18,6 @@
       keep-outputs = true
       keep-derivations = true
       fallback = true
-      # used by nix-dram
-      default-flake = flake:nixpkgs
     '';
   };
 }

overlays/overrides.nix

@@ -13,6 +13,7 @@ channels: final: prev: {
     signal-desktop
     starship
     deploy-rs
+    nix
 
     tdesktop
     arduino

profiles/dram/default.nix

@@ -1,5 +0,0 @@
-{ self, config, lib, pkgs, inputs, ... }:
-
-{
-  nix.package = inputs.nix-dram.packages.${pkgs.system}.nix-dram;
-}

shell/devos.nix

@@ -34,7 +34,7 @@ in
   '');
 
   commands = with pkgs; [
-    (devos nixUnstable)
+    (devos nix)
     (devos agenix)
     {
       category = "devos";