landlock: Improve the comment for domain_is_scoped

landlock: Improve the comment for domain_is_scoped

Currently it is not obvious what "scoped" mean, and the fact that the
function returns true when access should be denied is slightly surprising
and in need of documentation.

Cc: Tahera Fahimi <fahimitahera@gmail.com>
Signed-off-by: Tingmao Wang <m@maowtm.org>
Link: https://lore.kernel.org/r/06393bc18aee5bc278df5ef31c64a05b742ebc10.1766885035.git.m@maowtm.org
[mic: Fix formatting and improve consistency]
Signed-off-by: Mickaël Salaün <mic@digikod.net>