Fixes typo on comments
Fixes typo on comments

AnalyticalGraphicsInc/cesium,CesiumGS/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium,CesiumGS/cesium,likangning93/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium