BUILD: evports: remove a leftover from the dead_fd cleanup

Commit b1f29bc62 ("MINOR: activity/fd: remove the dead_fd counter") got
rid of FD_UPDT_DEAD, but evports managed to slip through the cracks and
wasn't cleaned up, thus it doesn't build anymore, as reported in github
issue #1467. We just need to remove the related lines since the situation
is already handled by the remaining conditions.

Thanks to Dominik Hassler for reporting the issue and confirming the fix.

This must be backported to 2.5 only.

src/ev_evports.c

@@ -250,10 +250,6 @@ static void _do_poll(struct poller *p, int exp, int wake)
 		 */
 		ret = fd_update_events(fd, n);
 
-		/* If the FD was already dead , skip it */
-		if (ret == FD_UPDT_DEAD)
-			continue;
-
 		/* disable polling on this instance if the FD was migrated */
 		if (ret == FD_UPDT_MIGRATED) {
 			if (!HA_ATOMIC_BTS(&fdtab[fd].update_mask, tid))