Bump DeterminateSystems/determinate-nix-action from 3 to 3.21.8

Bumps [DeterminateSystems/determinate-nix-action](https://github.com/determinatesystems/determinate-nix-action) from 3 to 3.21.8.
- [Release notes](https://github.com/determinatesystems/determinate-nix-action/releases)
- [Commits](https://github.com/determinatesystems/determinate-nix-action/compare/v3...v3.21.8)

---
updated-dependencies:
- dependency-name: DeterminateSystems/determinate-nix-action
  dependency-version: 3.21.8
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/flakehub-publish-rolling.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: "actions/checkout@v7"
         with:
           persist-credentials: false
-      - uses: "DeterminateSystems/determinate-nix-action@v3"
+      - uses: "DeterminateSystems/determinate-nix-action@v3.21.8"
       - uses: "DeterminateSystems/flakehub-push@main"
         with:
           name: "dwinkler1/nixCatsConfig"

.github/workflows/update.yml

@@ -15,7 +15,7 @@ jobs:
         with:
           hatchet-protocol: 'carve'
       - name: Install Determinate Nix
-        uses: DeterminateSystems/determinate-nix-action@v3
+        uses: DeterminateSystems/determinate-nix-action@v3.21.8
       - uses: cachix/cachix-action@v17
         with:
           name: rde