Fixing LoadSpriteFrame documentation

Fixing the documentation for Actor::LoadSpriteFrames() function. The ### sequence is meaningful  on doxygen, what caused the documentation to interpret it; see image.

![doxy](https://f.cloud.github.com/assets/2046959/2122474/3eeb46a2-9211-11e3-9e29-16ee2380a40d.png)

Since the number of ### didn't matter, I replaced it with a single one, what should fix the problem.