net-mgmt/zabbix42-*: Update to 4.2.6

Include upstream patch to fix daemon termination.
https://support.zabbix.com/browse/ZBX-16460 [1]

Changelog: https://www.zabbix.com/rn/rn4.2.6

PR: 239746 [1]
PR: 240193
Reported by: Christian Ullrich <chris@chrullrich.net> [1]
Approved by: Pakhom Golynga <pg@pakhom.spb.ru> (maintainer)