build(deps): bump DeterminateSystems/flake-checker-action

Bumps [DeterminateSystems/flake-checker-action](https://github.com/determinatesystems/flake-checker-action) from 5 to 7.
- [Release notes](https://github.com/determinatesystems/flake-checker-action/releases)
- [Commits](DeterminateSystems/flake-checker-action@v5...v7)

---
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/nix.yml

@@ -19,7 +19,7 @@ jobs:
                   # If you chose API tokens for write access OR if you have a private cache
                   authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
             - name: Keep the Flake up-to-date and healthy
-              uses: DeterminateSystems/flake-checker-action@v5
+              uses: DeterminateSystems/flake-checker-action@v7
               with:
                   fail-mode: true
             - run: nix flake check