grpcio 1.72.1 on Python PyPI

This is release gRPC Core 1.72.1 (gusto).

For gRPC documentation, see grpc.io. For previous releases, see Releases.

This release contains refinements, improvements, and bug fixes, with highlights listed below.

Python

Pin Cython to 3.1.1 #39609
- This solves several issues:
  1. #39588: Selecting unstable Cython releases when building gRPC Python artifacts.
  2. Using inconsistent Cython version in released platform-specific wheels within the same grpcio release.
  3. cython/cython#6878 Several published grpcio wheels were built with Cython 3.1.0 and are affected by Cython memory leak issue when using AsyncIO APIs (grpc.aio.*).
Fix Python 3.12 MacOS universal release artifact #39418