nix: merge mmsg to mangowc project

nix/default.nix

@@ -16,7 +16,6 @@
   enableXWayland ? true,
   meson,
   ninja,
-  mmsg,
   scenefx,
   wlroots_0_19,
   libGL,
@@ -60,7 +59,6 @@ in
 
     passthru = {
       providedSessions = ["mango"];
-      inherit mmsg;
     };
 
     meta = {
@@ -71,4 +69,4 @@ in
       maintainers = [];
       platforms = lib.platforms.unix;
     };
-  }
+  }

nix/nixos-modules.nix

@@ -21,12 +21,7 @@ in {
     environment.systemPackages =
       [
         cfg.package
-      ]
-      ++ (
-        if (builtins.hasAttr "mmsg" cfg.package)
-        then [cfg.package.mmsg]
-        else []
-      );
+      ];
 
     xdg.portal = {
       enable = lib.mkDefault true;