Revert "vte: 0.64.2 → 0.66.0"

This reverts commit 453edd71bfc0a7f56ad6e8969d80945ad1cc3c23.

It refuses to build with gcc9; that's the default on aarch64-linux,
and it would block the nixos-unstable channel. Discussion:
https://github.com/NixOS/nixpkgs/pull/142731#commitcomment-58711525

pkgs/development/libraries/vte/default.nix

···
 
 stdenv.mkDerivation rec {
   pname = "vte";
-  version = "0.66.0";
+  version = "0.64.2";
 
   outputs = [ "out" "dev" ];
 
   src = fetchurl {
     url = "mirror://gnome/sources/${pname}/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
-    sha256 = "sha256-0IE6wA+x102IhR52X3VdSWyD4JcJc1jqG6rbOLN7ezM=";
+    sha256 = "sha256-KzyCC2WmZ8HYhZuiBHi+Ym0VGcwxWdrCX3AzMMbQfhg=";
   };
 
   patches = [