Remove pseudo-terminals from ttys(5).

Remove pseudo-terminals from ttys(5).

When we had utmp(5), we had to list all the psuedo-terminals in ttys(5)
to make ttyslot(3) function properly. Now that pututxline(3) deals with
slot allocation internally (not based on TTY names), we don't need to
list all the TTYs on the system in ttys(5) to make user accounting work
properly.

This patch removes all the entries from the /etc/ttys files, but also
the pts(4) entries that were appended implicitly, which was added in
r154838.