chore(deps): update cachix/install-nix-action action to v31 (#660)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/update-readme.yaml

@@ -16,7 +16,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
         with:
           extra_nix_config: |
             accept-flake-config = true