gvinum(8): Fix a typo
On line 354, "go up from" is mistyped as "go up form".
Event: Advanced UNIX Programming Course (Fall’23) at NTHU.
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/951
(cherry picked from commit 2aa186b3b08bcf6e49b743329b2fa00897a1235f)