Cache Nix store

Version updated for nix-community/cache-nix-action to version v5.1.1.

• This action is used across all versions by 7 repositories.

Go to the GitHub Marketplace to find the latest changes.

Release notes

• Fix merging stores (https://github.com/nix-community/cache-nix-action/issues/31)

• nix-community
• GitHub Actions