ci(tools): update cachix/install-nix-action digest to a809471 (#59)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/flake.yml

@@ -23,7 +23,7 @@ jobs:
 
       - name: Install nix
         id: nix
-        uses: cachix/install-nix-action@7be5dee1421f63d07e71ce6e0a9f8a4b07c2a487 # v31
+        uses: cachix/install-nix-action@a809471b5c7c913aa67bec8f459a11a0decc3fce # v31
 
       - name: Update flake
         id: flake