Bump DeterminateSystems/nix-installer-action from 6 to 7 (#201)

Bumps [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) from 6 to 7.
- [Release notes](https://github.com/determinatesystems/nix-installer-action/releases)
- [Commits](DeterminateSystems/nix-installer-action@v6...v7)

---
updated-dependencies:
- dependency-name: DeterminateSystems/nix-installer-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>

.github/workflows/ci-nix.yml

@@ -17,7 +17,7 @@ jobs:
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v6
+      - uses: DeterminateSystems/nix-installer-action@v7
       - uses: DeterminateSystems/magic-nix-cache-action@v2
       - run: nix flake check
       - run: nix develop --command echo 'This step should be done before any other "nix develop" steps because of measuring Nix build time'