revert: "nix: add plymouth"

This reverts commit 84780229db3105ba94eea72fe1f18ea206358382.

nix/modules/boot.nix

@@ -3,32 +3,17 @@
 # theming of grub
 
 {
-  boot = {
-    loader.grub = {
-      theme = pkgs.stdenv.mkDerivation {
-        pname = "hyperfluent";
-        version = "v1.0.1";
-        src = pkgs.fetchFromGitHub {
-          owner = "Coopydood";
-          repo = "HyperFluent-GRUB-Theme";
-          rev = "62e525ea2aa250e3f37669d68eb355b6cc997d64";
-          hash = "sha256-Als4Tp6VwzwHjUyC62mYyiej1pZL9Tzj4uhTRoL+U9Q=";
-        };
-        installPhase = "cp -r nixos $out";
+  boot.loader.grub = {
+    theme = pkgs.stdenv.mkDerivation {
+      pname = "hyperfluent";
+      version = "v1.0.1";
+      src = pkgs.fetchFromGitHub {
+        owner = "Coopydood";
+        repo = "HyperFluent-GRUB-Theme";
+        rev = "62e525ea2aa250e3f37669d68eb355b6cc997d64";
+        hash = "sha256-Als4Tp6VwzwHjUyC62mYyiej1pZL9Tzj4uhTRoL+U9Q=";
       };
-    };
-
-    initrd.systemd.enable = true;
-
-    plymouth = {
-      enable = true;
-      theme = "rings";
-      themePackages = with pkgs; [
-        # By default we would install all themes
-        (adi1090x-plymouth-themes.override {
-          selected_themes = [ "rings" ];
-        })
-      ];
+      installPhase = "cp -r nixos $out";
     };
   };
 }