ci: bump DeterminateSystems/nix-installer-action from 15 to 16 (#2)

Bumps [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) from 15 to 16.
- [Release notes](https://github.com/determinatesystems/nix-installer-action/releases)
- [Commits](https://github.com/determinatesystems/nix-installer-action/compare/v15...v16)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/check.yml

@@ -11,5 +11,5 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v15
+      - uses: DeterminateSystems/nix-installer-action@v16
       - run: make check

.github/workflows/site.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v15
+      - uses: DeterminateSystems/nix-installer-action@v16
       - run: make build
       - name: Upload artifact
         id: deployment

.github/workflows/update-deps.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v15
+      - uses: DeterminateSystems/nix-installer-action@v16
       - run: nix develop --command make update
       - id: datetime
         run: |