font_manager calls nonexistent method FT2Font.get_fontsize

https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/font_manager.py#L476

The call to get_fontsize was adding in e34a333d00814124d3e19d462b9d78ac35e7a49a but cannot succeed because such a method was (AFAICT) never implemented on FT2Font.  Fortunately, font_manager probably never hits a nonscalable font because it that codepath only handles ttf/otf, but that should get cleaned up.