chore(deps): update cachix/cachix-action action to v16

Author: renovate[bot]

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: cachix/install-nix-action@v31
-      - uses: cachix/cachix-action@v15
+      - uses: cachix/cachix-action@v16
         with:
           name: devenv
       - name: Install devenv.sh