makefs/zfs: Don't set ZFS_NO_EXECS_DENIED in file flags

This flag was leftover from testing and should have been removed.

Approved by: re (cperciva)
PR: 274938
MFC after: 3 days
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 50565cf514d32ee02a24f420551c7e65631b0716)
(cherry picked from commit a8043cc0d49bec7bebc4afc43b8bf5f6ab730b23)