chore(injector): fix typo in injector documentation

Author: sqwishy

src/auto/injector.js

@@ -20,7 +20,7 @@
  *   // create an injector
  *   var $injector = angular.injector(['ng']);
  *
- *   // use the injector to kick of your application
+ *   // use the injector to kick off your application
  *   // use the type inference to auto inject arguments, or use implicit injection
  *   $injector.invoke(function($rootScope, $compile, $document){
  *     $compile($document)($rootScope);