nixopsUnstable: mark as broken

Unstable should probably be working towards updating to the most
recent version, so marking as broken, instead of using the pinned
version, like stable does.

see https://github.com/NixOS/nixpkgs/pull/52550
see https://github.com/NixOS/nixops/issues/1065
see https://github.com/NixOS/nixpkgs/issues/52547