Mention new rails in changelog

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

CHANGELOG

@@ -20,6 +20,7 @@ v 6.6.0
   - Show last commit for file when view file source
   - Restyle Issue#show page and MR#show page
   - Ability to filter by multiple labels for Issues page
+  - Rails version to 4.0.3
 v 6.5.1
   - Fix branch selectbox when create merge request from fork