build(deps): bump DeterminateSystems/magic-nix-cache-action from 4 to 6 (#79)

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 4 to 6.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v4...v6)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/Nix.yml

@@ -44,7 +44,7 @@ jobs:
         uses: DeterminateSystems/nix-installer-action@v10
 
       - name: "Nix Cache"
-        uses: DeterminateSystems/magic-nix-cache-action@v4
+        uses: DeterminateSystems/magic-nix-cache-action@v6
 
       - name: "Test Nix config"
         run: nix build --dry-run -L '.#${{ matrix.flake-attr }}' --show-trace