Remove Cargo.lock

[dario23]

This is a library, which should not have its Cargo.lock file committed, see e.g. https://doc.rust-lang.org/cargo/faq.html#why-do-binaries-have-cargolock-in-version-control-but-not-libraries.

Reverts commit 6e4f4200039e18a405e18f2ff8aa57a3769266c4