Removed stray pixels on zippy's death sprite

While playing as zippy I noted some stray pixels on her death sprite.
![screen shot 2014-02-15 at 12 47 41 pm](https://f.cloud.github.com/assets/4028391/2178686/57628f26-9674-11e3-9cd3-fa1a0c4f5dd6.png)

This removes those pixels.