build(7): fix references to svn(1) and svnlite(1)

Replace them with references to Git.

PR: 254937
Reported by: m.bueker@berlin.de
Approved by: 0mp (mentor)
Differential Revision: https://reviews.freebsd.org/D29949

(cherry picked from commit e444a4c677ee3e86038ba2179c4838f5f4b778cd)