Remove moot `version` property from bower.json

Per bower/bower.json-spec@a325da3

bower.json

@@ -1,6 +1,5 @@
 {
   "name": "AdminLTE",
-  "version": "2.1.2",
   "homepage": "http://almsaeedstudio.com",
   "authors": [
     "Abdullah Almsaeed <almasaeed2010@gmail.com>"