net/kafkacat: Update to 1.6.0

New options AVRO and JSON.
AVRO broken for now because of upstream problem with pkg-config

Changelog: https://github.com/edenhill/kafkacat/releases/tag/1.6.0

PR: 254093
Submitted by: Sergey Akhmatov <sergey@akhmatov.ru> (maintainer)