Remove unneeded field.
Remove unneeded field.

likangning93/cesium,CesiumGS/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,josh-bernstein/cesium,progsung/cesium,jasonbeverage/cesium,jasonbeverage/cesium,likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,josh-bernstein/cesium,YonatanKra/cesium,YonatanKra/cesium,likangning93/cesium,progsung/cesium,geoscan/cesium,CesiumGS/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,YonatanKra/cesium,kaktus40/cesium,YonatanKra/cesium,geoscan/cesium,kaktus40/cesium,CesiumGS/cesium