Revert "fix(ci): correctly build system"

This reverts commit 1d44a94079.

.github/workflows/main.yml

@@ -15,6 +15,4 @@ jobs:
           name: liminalos
           # If you chose API tokens for write access OR if you have a private cache
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
-      - run:
-          nix build .#nixosConfigurations.demeter.config.system.build.toplevel
-          --accept-flake-config
+      - run: nix build .#demeter --accept-flake-config