librdkafka: bump lz4 version & use version range for zstd & pkgconf

[SpaceIm]

Summary

Changes to recipe: lib/[version]

Motivation

Use version range for zstd & pkgconf since it's now allowed, and bump lz4 version in the meantime.

Details

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[conan-center-bot]

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Sorry, the system is under maintenance and it doesn't accept builds right now.

Motivation: Weekly scheduled maintenance

Please, check https://status.conan.io to obtain more information.
Thanks for your understanding and help with the Conan Center Index!