Don't configure mirrors for FreeBSD packages repository

Summary:
Packages are currently served from Ysul, while the mirrors config is broken.

As such, and as long packages are only served by ONE server, repository can
be configured to use a direct HTTPS connection without SRV records.

Fixes T1925.

Test Plan: Deployed to WindRiver

Reviewers: DorianWinty

Reviewed By: DorianWinty

Maniphest Tasks: T1925

Differential Revision: https://devcentral.nasqueron.org/D3249