quicksynergy: drop - #418001

       … while calling the 'throw' builtin
         at /var/lib/ofborg/checkout/repo/38dca4e3aa6bca43ea96d2fcc04e8229/builder/ofborg-core/pkgs/top-level/aliases.nix:1683:18:
         1682|   quickserve = throw "'quickserve' has been removed because its upstream is unavailable"; # Added 2025-05-10
         1683|   quicksynergy = throw "'quicksynergy' has been removed due to lack of maintenance upstream. Consider using 'deskflow' instead."; # Added 2025-06-18
             |                  ^
         1684|   qv2ray = throw "'qv2ray' has been removed as it was unmaintained"; # Added 2025-06-03

       error: 'quicksynergy' has been removed due to lack of maintenance upstream. Consider using 'deskflow' instead.