Remove setting the stdio file handle to nonblocking

[multiplemonomials]

As it turns out, this was causing issues because stdin and stdout are the same file handle, so stdout was also being set to nonblocking. And setting stdout to nonblocking meant that once the BufferedSerial TX buffer filled up, remaining characters printed would get deleted, so the entire bar graph was not being printed.

I think I originally added this code to try and implement the "press any key to exit" detection, but now this can be done via readable() anyway.