Update github action

Author: RCoeurjoly

.github/workflows/nix-github-actions.yml

@@ -9,5 +9,5 @@ jobs:
     - uses: actions/checkout@v4
       with:
        submodules: true
-    - uses: cachix/install-nix-action@v25
+    - uses: cachix/install-nix-action@v26
     - run: nix build '.?submodules=1'