libpng: update zlib version range

[sykhro]

This recipe is currently blocking a zlib update.
Sorry, saw the documentation update just now.

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• I've read the contributing guidelines.
• I've used a recent Conan client version close to the currently deployed.
• I've tried at least one configuration locally with the conan-center hook activated.

[github-actions]

🤖 Beep Boop! This pull request is making changes to 'recipes/libpng//'.

👋 @Hopobcn you might be interested. 😉

[ghost]

I detected other pull requests that are modifying libpng/all recipe:

• libpng: use version range for zlib #19648
• libpng: add with_zlibng option #18280

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[sykhro]

Whoops, I'll close this one.

[AbrilRBS]

Hi @sykhro thanks a lot for your contribution.

In order to avoid missing binaries & conflicts, we're holding off from merging zlib bumps to versions ranges. We are handling this internally and will create the appropriate PRs in order, and we'll take care of the rest of the recipes, no need to open new PRs with them :)

(See the note in here)