trivial: move config file change note down

Author: kay-kim

source/reference/configuration-options.txt

@@ -4,14 +4,6 @@ Configuration File Options
 
 .. default-domain:: mongodb
 
-.. important::
-
-   .. versionchanged:: 2.6
-      MongoDB 2.6 introduces a YAML-based configuration file format.
-      The :v2.4:`2.4 configuration file format
-      </reference/configuration-options>` remains for backward
-      compatibility.
-
 The following page describes the configuration options available in
 MongoDB |version|. For configuration file options for other versions of
 MongoDB, see the appropriate version of the MongoDB Manual.
@@ -36,7 +28,13 @@ file.
 File Format
 ~~~~~~~~~~~
 
-.. versionchanged:: 2.6
+.. important::
+
+   .. versionchanged:: 2.6
+      MongoDB 2.6 introduces a YAML-based configuration file format.
+      The :v2.4:`2.4 configuration file format
+      </reference/configuration-options>` remains for backward
+      compatibility.
 
 MongoDB configuration files use the `YAML <http://www.yaml.org>`_ format
 [#yaml-json]_.