Integration tests are broken

[bbatsov]

They all fail during setup:

Run purcell/setup-emacs@master
Run /Users/runner/work/_actions/purcell/setup-emacs/master/install.sh
Installing Nix
Configuring build cache and installing Emacs
  copying path '/nix/store/4ab6vrcph07w6ra79bc04fy8bbcmb9r0-source' from 'https://cache.nixos.org/'...
  error: flake 'github:purcell/nix-emacs-ci' does not provide attribute 'packages.aarch64-darwin.emacs-26-3', 'legacyPackages.aarch64-darwin.emacs-26-3' or 'emacs-26-3'
         Did you mean one of emacs-29-3, emacs-28-1, emacs-28-2, emacs-29-1 or emacs-29-2?

@ikappaki can please check what changed with the images?

[vemv]

See also purcell/nix-emacs-ci#267