nix: update ci

.github/workflows/nix.yml

@@ -12,9 +12,5 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@main
-        with:
-          extra-conf: |
-            trusted-substituters = https://gepetto.cachix.org
-            trusted-public-keys = gepetto.cachix.org-1:toswMl31VewC0jGkN6+gOelO2Yom0SOHzPwJMY2XiDY=
       - uses: DeterminateSystems/magic-nix-cache-action@main
-      - run: nix build
+      - run: nix build --accept-flake-config