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/continuous-integration.yml

@@ -39,7 +39,7 @@ jobs:
         fetch-depth: 0
 
     - name: Installing Nix
-      uses: cachix/install-nix-action@v25
+      uses: cachix/install-nix-action@v26
       with:
         nix_path: nixpkgs=channel:nixos-unstable
         extra_nix_config: |

.github/workflows/update-flake-lock.yml

@@ -11,7 +11,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
       - name: Install Nix
-        uses: cachix/install-nix-action@v25
+        uses: cachix/install-nix-action@v26
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}