[skip ci] Tweak availability comment wording.
[skip ci] Tweak availability comment wording.
CesiumGS/cesium,CesiumGS/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,likangning93/cesium,CesiumGS/cesium,CesiumGS/cesium,likangning93/cesium