Remove moot `version` property from bower.json

Per bower/bower.json-spec@a325da3

bower.json

@@ -1,6 +1,5 @@
 {
   "name": "babylonjs",
-  "version": "2.1.0",
   "description": "Babylon.js is a complete JavaScript framework for building 3D games with HTML 5 and WebGL",
   "main": "babylon.2.1.js",
   "homepage": "https://www.babylonjs.com",