dns/unbound: upgrade to 1.25.2

This release consolidates security fixes for issues reported over
a period of time. There are fixes for CVE-2026-14586, CVE-2026-32665,
CVE-2026-40691, CVE-2026-41637, CVE-2026-42955, CVE-2026-44621,
CVE-2026-44687, CVE-2026-44690, CVE-2026-46582, CVE-2026-50045,
CVE-2026-50046, CVE-2026-50243, CVE-2026-50248, CVE-2026-50251,
CVE-2026-50252, CVE-2026-52863, CVE-2026-54478, CVE-2026-55708,
CVE-2026-55717, CVE-2026-55973, CVE-2026-55990, CVE-2026-55991,
CVE-2026-56416 and CVE-2026-56444.

https://github.com/NLnetLabs/unbound/releases/tag/release-1.25.2

PR: ports/296982
Approved by: maintainer (Jaap Akkerhuis)

(cherry picked from commit f9133ceced2abb26c8e7722df2ac66b9bf694280)