Dis-allow borrow_deref_ref with new PyO3 release

[jvmncs]

Per the following issues, there is a problem with PyO3's pyfunction macro triggering a faulty warning in clippy:

• Can't ignore clippy::borrow_deref_ref rust-lang/rust-clippy#8971
• pyfunction: use extract_argument with holder to avoid extractext PyO3/pyo3#2503

In #21 we force allow-ed the faulty warning. The PyO3 PR merges a fix, but it has not yet made it's way into a release. Once a new version of PyO3 has been published, we should revert the lint change we did in #21 by dis-allowing the lint warning for borrow_deref_ref.