build(deps): bump DeterminateSystems/nix-installer-action from 5 to 6

Bumps [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) from 5 to 6.
- [Release notes](https://github.com/determinatesystems/nix-installer-action/releases)
- [Commits](DeterminateSystems/nix-installer-action@v5...v6)

---
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]>

.github/workflows/update.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Install Nix
-        uses: DeterminateSystems/nix-installer-action@v5
+        uses: DeterminateSystems/nix-installer-action@v6
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
       - name: Update flake.lock