archivers/py-borgbackup11: fix pkg-message instructions

which were suggesting to add the loader.conf variable fusefs_load
to rc.conf instead via sysrc.

Reported by: zero1@zaclys.net
PR: 278429
MFH: 2024Q2

(cherry picked from commit 5c457fb00e613885e4aab48afd69a6fe129a3d6d)