Tyra Banks got the call from TV execs to change the format of “America’s Next Top Model” while she was in class at Harvard Business School. “I got a note that said you need to get out of class and take this call. My boss said . . . there are no sacred cows, and you have to do some crazy changes. It was a mandate.” Page Six revealed in April that “ANTM” veteran co-stars J. Alexander, Jay Manuel and Nigel Barker were dumped to reinvigorate the long-running show. The new season debuts tonight on CW.