net-mgmt/zabbix5: Update to 5.0.12

Relnotes: https://www.zabbix.com/rn/rn5.0.12
Approved by: Pakhom Golynga (maintainer)
Differential Revision: https://reviews.freebsd.org/D30800

(cherry picked from commit 415a9bf401028f22e5488cd31c0353150a163691)