Work around PyO3/pyo3#2555 and remove stale allow.

[ci skip-build-wheels]

src/rust/engine/src/lib.rs

@@ -24,10 +24,8 @@
 #![allow(clippy::new_without_default, clippy::new_ret_no_self)]
 // Arc<Mutex> can be more clear than needing to grok Orderings:
 #![allow(clippy::mutex_atomic)]
-// We only use unsafe pointer dereferences in our no_mangle exposed API, but it is nicer to list
-// just the one minor call as unsafe, than to mark the whole function as unsafe which may hide
-// other unsafeness.
-#![allow(clippy::not_unsafe_ptr_arg_deref)]
+// TODO: See https://github.com/PyO3/pyo3/issues/2555
+#![allow(clippy::borrow_deref_ref)]
 #![type_length_limit = "43757804"]
 
 #[macro_use]