Update GitHub Workflow

Bump install-nix-action to v31 (to get a newer nix binary)

Author: angerman

.github/workflows/update-hash.yaml

@@ -50,7 +50,7 @@ jobs:
 
       - name: Install Nix
         if: steps.check-etag.outputs.changed == 'true'
-        uses: cachix/install-nix-action@v22
+        uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           extra_nix_config: |