[chore(ci)](deps): Bump DeterminateSystems/flake-checker-action

Bumps [DeterminateSystems/flake-checker-action](https://github.com/determinatesystems/flake-checker-action) from 7 to 9.
- [Release notes](https://github.com/determinatesystems/flake-checker-action/releases)
- [Commits](DeterminateSystems/flake-checker-action@v7...v9)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/nix.yml

@@ -44,7 +44,7 @@ jobs:
         uses: DeterminateSystems/magic-nix-cache-action@v6
 
       - name: Check Nix flake inputs
-        uses: DeterminateSystems/flake-checker-action@v7
+        uses: DeterminateSystems/flake-checker-action@v9
         with:
           ignore-missing-flake-lock: false
           fail-mode: true