improve sessionVariable declaration

Without this, on wayland I cannot access these vars from the Terminal

modules/home/desktop/default.nix

@@ -26,7 +26,7 @@ in
   ];
 
   config = lib.mkIf cfg.enable {
-    # systemd.user.sessionVariables.GTK_THEME = "Catppuccin-Mocha-Compact-Blue-dark";
+    # home.sessionVariables.GTK_THEME = "Catppuccin-Mocha-Compact-Blue-dark";
     prism = {
       enable = true;
       wallpapers = ./wallpapers;