Remove useless -t

Remove useless -t

"Make if.c kvm free by fetching the interface stats via sysctl ..."
if.c r1.56 in 2008 neutered the -d and -t flags.

-d functionality was eventually restored with if.c r1.76 in 2015.

-t has been printing zeroes for over fourteen now; this cannot have been
useful to anyone and noone complained about a wrong watchdog timer values.

Remove -t entirely without printing a warning;  `netstat -t ...' now fails.

Feedback jsg
OK jsg bluhm