chore(deps): update determinatesystems/nix-installer-action action to v21

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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
         run: pnpm install --frozen-lockfile
 
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v20
+        uses: DeterminateSystems/nix-installer-action@v21
         with:
           extra-conf: |
             accept-flake-config = true