tools/sysdoc: Chase sysctl rename
PR: 285591
Reviewed by: glebius
Fixes: 94df3271d6b2 ("Rename net.inet.ip.check_interface to rfc1122_strong_es and document it.")
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D49486
(cherry picked from commit d45d070e5475466ceac8057f2e7558055267fb1b)