Reference the actual location of the documentation

Author: Grégoire Paris

README.md

@@ -14,7 +14,7 @@ previous version of the component will break with this version.
 Resources
 ---------
 
-  * [Documentation](https://symfony.com/doc/current/components/ldap/index.html)
+  * [Documentation](https://symfony.com/doc/current/components/ldap)
   * [Contributing](https://symfony.com/doc/current/contributing/index.html)
   * [Report issues](https://github.com/symfony/symfony/issues) and
     [send Pull Requests](https://github.com/symfony/symfony/pulls)