net/fort: Update to 1.6.2

- Update to 1.6.2
- Changelog: https://github.com/NICMx/FORT-validator/releases/tag/1.6.2

While here, fix building with libxml2 2.13.1 [1].  This patch will be in
the next upstream release.

Approved by:	Toni Kalombo <toni@devboks.com> (maintainer, implicit)
Reported by:	diizzy [1]
PR:             279898 [1]