Protocol Buffers Version 21.9 is Released!

[Adam Cozzette]

This version includes the following non-breaking changes:

C++
- Update zlib to 1.2.13 (#10819)

Python
 - Target MacOS 10.9 to fix #10799 (#10807)

Ruby
 - Replace libc strdup usage with internal impl to restore musl compat (#10818)

You can view the release on GitHub.

If you experience any issues with the release, please file a bug or post on the ProtocolBuffers forum.