build(deps): bump DeterminateSystems/magic-nix-cache-action from 8 to 9 (#95)

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 8 to 9.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v8...v9)

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

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

Author: dependabot[bot]

.github/workflows/flake-check.yaml

@@ -12,5 +12,5 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: cachix/install-nix-action@v30
-      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - uses: DeterminateSystems/magic-nix-cache-action@v9
       - run: nix flake check