Bump the nix-actions group with 2 updates

Bumps the nix-actions group with 2 updates: [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) and [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action).


Updates `DeterminateSystems/nix-installer-action` from 10 to 11
- [Release notes](https://github.com/determinatesystems/nix-installer-action/releases)
- [Commits](DeterminateSystems/nix-installer-action@v10...v11)

Updates `DeterminateSystems/magic-nix-cache-action` from 4 to 6
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v4...v6)

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

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

.github/workflows/ci-nix.yml

@@ -27,8 +27,8 @@ jobs:
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v10
-      - uses: DeterminateSystems/magic-nix-cache-action@v4
+      - uses: DeterminateSystems/nix-installer-action@v11
+      - uses: DeterminateSystems/magic-nix-cache-action@v6
       - 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'
       - name: Log current versions