fix: update gh action nix install (#355)

1. update nix install action version

Should fix the CI failures

Author: ghthor

.github/workflows/test.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v25
+      - uses: cachix/install-nix-action@v31.6.1
         with:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
           nix_path: nixpkgs=channel:nixos-unstable