ci(tools): update cachix/install-nix-action action to v31 (#127)

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

Author: renovate[bot]

.github/workflows/flake.yml

@@ -22,7 +22,7 @@ jobs:
 
       - name: Install nix
         id: nix
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
 
       - name: Update flake
         id: flake