refactor: use nix-flatpak instead of nixpak

I went to close into the sun, again

modules/home-manager/zen-browser.nix

@@ -1,27 +0,0 @@
-{
-  config,
-  lib,
-  pkgs,
-  self,
-  ...
-}: let
-  cfg = config.programs.zen-browser;
-in {
-  # This could be extended when https://github.com/NixOS/nixpkgs/issues/327982 is
-  # fixed.
-  # mkFirefoxModule (https://github.com/nix-community/home-manager/blob/f99c704fe3a4cf8d72b2d568ec80bc38be1a9407/modules/programs/firefox/mkFirefoxModule.nix)
-  # can be used to create a module that handles extensions just like firefox and librewolf
-  # modules.
-  options.programs.zen-browser = with lib; {
-    enable = mkEnableOption "";
-    package = mkOption {
-      type = with types; package;
-      default = self.packages.${pkgs.system}.zen-browser;
-    };
-  };
-  config = lib.mkIf cfg.enable {
-    home.packages = [
-      cfg.package
-    ];
-  };
-}