kern_reboot(9): belatedly bump .Dd

Fixes:	4e78a766f6 ("kern_reboot(): don't clear kdb_active")
Sponsored by:	The FreeBSD Foundation

share/man/man9/kern_reboot.9

@@ -39,7 +39,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd March 20, 2023
+.Dd November 23, 2023
 .Dt REBOOT 9
 .Os
 .Sh NAME