Bump cachix/install-nix-action from 24 to 25 (#31)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 24 to 25.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@7ac1ec2...6004951)

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

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

.github/workflows/flake-update.yml

@@ -12,7 +12,7 @@ jobs:
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
 
       - name: Install Nix
-        uses: cachix/install-nix-action@7ac1ec25491415c381d9b62f0657c7a028df52a7 # v24
+        uses: cachix/install-nix-action@6004951b182f8860210c8d6f0d808ec5b1a33d28 # v25
 
       - name: Update flake.lock
         uses: DeterminateSystems/update-flake-lock@v20