#1548 Patch: update zlib 1.2.8 -> 1.3.1

[Federico Perini]

This patch is extracted from #1546 for clarity.

C::B ships an earlier zlib version (1.2.8 I believe) that isn’t supported on modern macOS toolchains; it seems the only solution is to update to 1.3.1 (see i.e. https://github.com/google-ai-edge/mediapipe/issues/5943), I think this would be beneficial anyways.

It seems like there are no API changes between the two zlib versions.
zlib is in the help_plugin folder, I don't know if it is also used elsewhere or only by the help plugin.

[Morten MacFly]

Applied in SVN, [r13716] . Thank you!