build(deps): bump DeterminateSystems/magic-nix-cache-action

Bumps the actions group with 1 update: [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action).


Updates `DeterminateSystems/magic-nix-cache-action` from 7 to 8
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v7...v8)

---
updated-dependencies:
- dependency-name: DeterminateSystems/magic-nix-cache-action
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

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

.github/workflows/nix.yaml

@@ -23,6 +23,6 @@ jobs:
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@v14
       - name: Setup Nix Cache
-        uses: DeterminateSystems/magic-nix-cache-action@v7
+        uses: DeterminateSystems/magic-nix-cache-action@v8
       - run: nix build
       - run: nix flake check