docs($injector): injectors aren't functions

Closes angular#9453

Author: thorn0

src/auto/injector.js

@@ -7,13 +7,13 @@
  * @kind function
  *
  * @description
- * Creates an injector function that can be used for retrieving services as well as for
+ * Creates an injector object that can be used for retrieving services as well as for
  * dependency injection (see {@link guide/di dependency injection}).
  *
 
  * @param {Array.<string|Function>} modules A list of module functions or their aliases. See
  *        {@link angular.module}. The `ng` module must be explicitly added.
- * @returns {function()} Injector function. See {@link auto.$injector $injector}.
+ * @returns {function()} Injector object. See {@link auto.$injector $injector}.
  *
  * @example
  * Typical usage