remove redundant draw command in CinderViewCocoaTouch

this drawView is unnecessary, as drawing will occur in sync via the display link.  Also, in some rare cases (such as in [this post](https://forum.libcinder.org/topic/device-orientation-animation-flash-of-incorrect-positioning-apprewrite-branch) about fancy orientation animations), it may cause an additional flicker when the underlining CALayer mechanisms have not yet performed their adjustments.

After removing this drawView and experimenting with the code on that link, I noticed far fewer flickers.