Enable mangohud on Vanguard by default (Vulkan only)

Remove steamscope script

system/Vanguard.nix

@@ -6,6 +6,7 @@
 }:
 {
   imports = [ ./desktop.nix ];
+  environment.sessionVariables.MANGOHUD = 1;
   home-manager.users.${username} = {
     home.packages = with pkgs; [
       krita
@@ -22,11 +23,6 @@
       lutris
       cartridges
       prismlauncher
-      (writeShellScriptBin "steamscope" ''
-        swaymsg output DP-1 adaptive_sync on
-        gamescope -w 2560 -h 1440 -W 2560 -H 1440 -r 120 --adaptive-sync --fullscreen --mangoapp -e -- steam -gamepadui
-        swaymsg output DP-1 adaptive_sync off
-      '')
     ];
     programs.obs-studio = {
       enable = true;