ObsoleteFiles: Remove mount_fusefs.8 entry

This causes make delete-old to delete the manual for mount_fusefs(8) on
(zfs) systems that do not (need) MANCOMPRESS.

MFC after: 3 days
Reviewed by: carlavilla, imp
Approved by: carlavilla (mentor)
Differential Revision: https://reviews.freebsd.org/D49667

(cherry picked from commit 7d2b5f3d2a5127a584d2af912ea0e9fd00f417f0)