Fix output of createuser --help with --valid-until

The argument required by --valid-until, a timestamp string, was missing
in the description of --help.

Author: Shinoda, Noriyoshi
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/DM4PR84MB1734A6CE3839A68B59BEA599EE899@DM4PR84MB1734.NAMPRD84.PROD.OUTLOOK.COM

Author: michaelpq

src/bin/scripts/createuser.c

@@ -426,7 +426,8 @@ help(const char *progname)
 	printf(_("  -R, --no-createrole       role cannot create roles (default)\n"));
 	printf(_("  -s, --superuser           role will be superuser\n"));
 	printf(_("  -S, --no-superuser        role will not be superuser (default)\n"));
-	printf(_("  -v, --valid-until         password expiration date for role\n"));
+	printf(_("  -v, --valid-until=TIMESTAMP\n"
+			 "                            password expiration date for role\n"));
 	printf(_("  -V, --version             output version information, then exit\n"));
 	printf(_("  --interactive             prompt for missing role name and attributes rather\n"
 			 "                            than using defaults\n"));