chore(deps): bump cachix/install-nix-action from 25 to 26

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 25 to 26.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@v25...v26)

---
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

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/flake-checker-action@v5
-      - uses: cachix/install-nix-action@v25
+      - uses: cachix/install-nix-action@v26
         with:
           github_access_token: ${{ secrets.GH_TOKEN }}
       - uses: cachix/cachix-action@v14