mono: don't propagate a dependency to glib-dev

This was added in 2005 back in r51ce4ea2. This was not commented or
explained anywhere, and it does not seem to be necessary anymore
according to some quick testing I did.

Reduces mono closure size by ~100M.

pkgs/development/compilers/mono/generic.nix

@@ -21,8 +21,6 @@ stdenv.mkDerivation rec {
     ]
     ++ (stdenv.lib.optionals stdenv.isDarwin [ Foundation libobjc ]);
 
-  propagatedBuildInputs = [glib];
-
   configureFlags = [
     "--x-includes=${libX11.dev}/include"
     "--x-libraries=${libX11.out}/lib"