gnome3.totem: disable vala plug-ins again

Apparently the intermittent build failure is still there,
not sure why I thought it was fixed.

Closes: https://github.com/NixOS/nixpkgs/issues/43518

pkgs/desktops/gnome-3/core/totem/default.nix

@@ -34,6 +34,10 @@ stdenv.mkDerivation rec {
 
   mesonFlags = [
     "-Dwith-nautilusdir=lib/nautilus/extensions-3.0"
+    # https://bugs.launchpad.net/ubuntu/+source/totem/+bug/1712021
+    # https://bugzilla.gnome.org/show_bug.cgi?id=784236
+    # https://github.com/mesonbuild/meson/issues/1994
+    "-Denable-vala=no"
   ];
 
   wrapPrefixVariables = [ "PYTHONPATH" ];