mac_bsdextended: Use SYSCTL VARIABLES section

All the other man pages, except iicbus(4), use .Sh SYSCTL VARIABLES for
documentig sysctls. iicbus(4) has a legitmate reason for varying,
though.

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share/man/man4/mac_bsdextended.4

@@ -28,7 +28,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 21, 2005
+.Dd October 11, 2024
 .Dt MAC_BSDEXTENDED 4
 .Os
 .Sh NAME
@@ -87,7 +87,7 @@ This means that not all rules are applied,
 only the first matched rule; thus if
 Rule A allows access and Rule B blocks
 access, Rule B will never be applied.
-.Ss Sysctls
+.Sh SYSCTL VARIABLES
 The following sysctls may be used to tweak the behavior of
 .Nm :
 .Bl -tag -width indent