Try a different nix installer

Author: dmjio

.github/workflows/main.yml

@@ -11,6 +11,10 @@ jobs:
     if: github.ref != 'refs/heads/master'
     steps:
      - uses: DeterminateSystems/nix-installer-action@main
+     - uses: actions/checkout@v3.5.3
+     - uses: cachix/install-nix-action@v25
+       with:
+         nix_path: nixpkgs=channel:nixpkgs-unstable
 
      - name: Nix channel update
        run: nix-channel --update