docs($logProvider): debugEnabled is a method not a property

Closes angular#7824

Author: petebacondarwin

src/ng/log.js

@@ -47,7 +47,7 @@ function $LogProvider(){
       self = this;
 
   /**
-   * @ngdoc property
+   * @ngdoc method
    * @name $logProvider#debugEnabled
    * @description
    * @param {boolean=} flag enable or disable debug level messages