Building with maturin shows new warring

[igalshilman]

running maturin dev -E ... emits warning of type:

warning: unexpected `cfg` condition value: `gil-refs`
   --> src/lib.rs:188:1
    |
188 | / create_exception!(
189 | |     restate_sdk_python_core,
190 | |     VMException,
191 | |     pyo3::exceptions::PyException,
192 | |     "Restate VM exception."
193 | | );
    | |_^
    |
    = note: no expected values for `feature`
    = help: consider adding `gil-refs` as a feature in `Cargo.toml`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default
    = note: this warning originates in the macro `$crate::impl_exception_boilerplate` which comes from the expansion of the macro `create_exception` (in Nightly builds, run with -Z macro-backtrace for more info)

``

[slinkydeveloper]

Looked at this, and it seems the last py03 version fixes it. I think we can upgrade safely, py03 last version drops support for Python 3.7 and 3.8, but our wheel is already declaring minimum python version 3.11

[slinkydeveloper]

Looked a bit into bumping to pyo3 latest version, there's few things to check out here https://pyo3.rs/v0.23.0/migration#from-022-to-023. Will do that when adapting to protocol v4