Switch to latest branch of the FreeBSD packages repository

Summary:
This allows to get more up-to-date packages, regardless of ports maintainers
decision to backport or not security fixes to the quarterly branch.

Fixes T2032.

Test Plan: Deploy on WindRiver

Reviewers: DorianWinty

Reviewed By: DorianWinty

Maniphest Tasks: T2032

Differential Revision: https://devcentral.nasqueron.org/D3593