Removes the Video element from the DOM by calling parentNode.removeChild on itself.
Also removes the autoplay and src attributes and nulls the Video reference.
You should not call this method if you were playing a video from the Video Cache that you wish to play again in your game, or if another Video object is also using the same video.
If you loaded an external video via Video.loadURL
then you should call this function
to clear up once you are done with the instance.