Cygwin: pty: Remove close() call just before reopening slave.

- After commit da4ee7d60b9ff0bcdc081609a4467adb428d58e6, the issue
  reported in https://www.cygwin.com/ml/cygwin/2020-01/msg00209.html
  occurs. This patch fixes the issue.

winsup/cygwin/fhandler_tty.cc

@@ -1281,7 +1281,6 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len)
     {
       termios_printf ("GetConsoleMode failed, %E");
       /* Re-open handles */
-      this->close ();
       this->open (0, 0);
       /* Fix pseudo console window size */
       this->ioctl (TIOCSWINSZ, &get_ttyp ()->winsize);