mac(4): also list jails in the example enumeration of objects

The prison may also be considered part of the subject by way of its
ucred association, but I don't think this is significantly different
enough today than before recent work -- policies could have always
taken them into account, and some did (e.g., mac_bsdextended).

Reported by:	olce
Reviewed by:	olce, ziaee
Differential Revision:	https://reviews.freebsd.org/D54748

share/man/man4/mac.4

@@ -28,7 +28,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd January 15, 2026
+.Dd January 16, 2026
 .Dt MAC 4
 .Os
 .Sh NAME
@@ -68,7 +68,7 @@ Currently, the following MAC policy modules are shipped with
 .El
 .Ss MAC Labels
 Each system subject (processes, sockets, etc.) and each system object
-(file system objects, sockets, etc.) can carry with it a MAC label.
+(file system objects, jails, sockets, etc.) can carry with it a MAC label.
 MAC labels contain data in an arbitrary format
 taken into consideration in making access control decisions
 for a given operation.