security/strongswan: Update 6.0.3 => 6.0.4
Changelog:
https://github.com/strongswan/strongswan/releases/tag/6.0.4
PR: 293003
Approved by: strongswan@Nanoteq.com (maintainer, timeout > 3 weeks)
MFH: 2026Q1
(cherry picked from commit f1fee394eae0378de1cb716704b43061d880ba6c)