build(deps): bump cachix/install-nix-action from 26 to 27

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 26 to 27.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@8887e59...ba0dd84)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/CI.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@44c2b7a8a4ea60a981eaca3cf939b5f4305c123b
-      - uses: cachix/install-nix-action@8887e596b4ee1134dae06b98d573bd674693f47c
+      - uses: cachix/install-nix-action@ba0dd844c9180cbf77aa72a116d6fbc515d0e87b
       - name: Build
         run: nix-shell --pure --run 'make SPHINXOPTS='-W' html'
   build_docker_image_theme_tuleap_org: