bsdinstall: prefer HTTP

In 2024, users are more likely to have working HTTP than working FTP.
Present http://ftp.FreeBSD.org as the first option in the installer.
Keep ftp://ftp.FreeBSD.org as the second option.

MFC after: 3 weeks

(cherry picked from commit 9c59988175ffd6b42c6927c0939e13abc43f7344)