chore(deps): update cachix/install-nix-action action to v31 (#620)

Author: renovate[bot]

.github/workflows/gh-pages.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
       - name: Install Nix
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
       - name: Build GitHub Pages
         id: build
         run: |