Bump cachix/cachix-action from 10 to 12 (#104)

Bumps [cachix/cachix-action](https://github.com/cachix/cachix-action) from 10 to 12.
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](cachix/cachix-action@v10...v12)

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

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

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

.github/workflows/nix.yml

@@ -27,7 +27,7 @@ jobs:
             experimental-features = nix-command flakes
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
       - name: Setup Cachix
-        uses: cachix/cachix-action@v10
+        uses: cachix/cachix-action@v12
         with:
           name: igm
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"