man: Update the date

[skip ci]

Author: fxlb

tcpdump.1.in

@@ -20,7 +20,7 @@
 .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 .\"
-.TH TCPDUMP 1  "21 October 2023"
+.TH TCPDUMP 1  "19 December 2023"
 .SH NAME
 tcpdump \- dump traffic on a network
 .SH SYNOPSIS