update changelog

Author: jessekrubin

CHANGELOG.md

@@ -15,6 +15,7 @@ To see unreleased changes, please see the CHANGELOG on the main branch.
   Trait `Runtime` now requires `spawn_blocking` function,
   `future_into_py` functions now require future return type to be `Send`.
   [#60](https://github.com/PyO3/pyo3-async-runtimes/pull/60)
+- Change pyo3 `downcast` calls to `cast` calls [#65](https://github.com/PyO3/pyo3-async-runtimes/pull/65)
 
 ## [0.26.0] - 2025-09-02