Because there is no crate for Spartan2 repo, you need to clone it in the same directory
git clone https://github.com/akalmykov/halo2-spartan.git
git clone [email protected]:microsoft/Spartan2.git
cd halo2-spartan
cargo run --example spartan -- --name spartan -k 8 prove
cargo run --example spartan -- --name spartan -k 8 verify