deps: update pyo3 to newest version

[theHamsta]

This allows using pywebnn with Python 3.14 without needing to set any environment variables that allow usage with unknown Python versions.

All our dependencies are not up-to-date at the moment.

I'm not familiar to the project so I don't know whether I broke anything. These tests are failing before and after the change.

FAILED tests/test_python_api.py::test_async_dispatch - Failed: async def functions are not natively supported.
FAILED tests/test_python_api.py::test_async_tensor_read_write - Failed: async def functions are not natively supported.
FAILED tests/test_python_api.py::test_async_concurrent_operations - Failed: async def functions are not natively supported.
FAILED tests/test_python_api.py::test_async_dispatch_with_actual_computation - Failed: async def functions are not natively supported.
FAILED tests/test_python_api.py::test_async_context_properties - Failed: async def functions are not natively supported.

EDIT: was just because of missing pytest-asyncio

[theHamsta]

FromPyObject requires Clone. DeviceTensorHandle is not Clone at the moment. Would need to switch from Box<dyn backend> to Arc<dyn backend>

[theHamsta]

Async support https://pyo3.rs/v0.28.2/async-await

[theHamsta]

Seems that setuptools-rust is now recommended instead of the extension-module feature https://pyo3.rs/v0.28.2/features.html#extension-module