changelog.md: 2.5, not 2.6

changelog.md

@@ -3,7 +3,7 @@ Changelog for the [`directory`][1] package
 
 ## 1.3.0.1 (January 2017)
 
-  * Relax Win32 version bounds to support 2.6.
+  * Relax Win32 version bounds to support 2.5.
     ([#67](https://github.com/haskell/directory/pull/67))
 
 ## 1.3.0.0 (December 2016)