.github: Bump DeterminateSystems/flake-checker-action from 8 to 9

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

---
updated-dependencies:
- dependency-name: DeterminateSystems/flake-checker-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/check.yml

@@ -13,7 +13,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Check Nix flake inputs
-        uses: DeterminateSystems/flake-checker-action@v8
+        uses: DeterminateSystems/flake-checker-action@v9
     # - uses: cachix/install-nix-action@v23
     #   with:
     #     install_url: https://nixos.org/nix/install