ci: update nix install action on gh workflow

Author: blaggacao

.github/workflows/gh-pages.yaml

@@ -13,11 +13,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
-      - uses: nixbuild/nix-quick-install-action@v21
-        with:
-          nix_conf: |
-            experimental-features = nix-command flakes
-            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+      - uses: nixbuild/nix-quick-install-action@v25
 
       - run: nix develop .#book -c mdbook build ./docs