build(deps): bump cachix/cachix-action from 10 to 12

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

.github/workflows/Optional-Nix-dev-env-main.yml

@@ -36,7 +36,7 @@ jobs:
       with:
         nix_path: nixpkgs=channel:nixos-unstable
     - name: "Install Cachix"
-      uses: cachix/cachix-action@v10
+      uses: cachix/cachix-action@v12
       with:
         name: ${{ env.cachixAccount }}
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'