CHANGELOG: Update.

Author: byohay

CHANGELOG.md

@@ -16,6 +16,10 @@
   [Max Langer](https://github.com/mangerlahn)
   [#853](https://github.com/CocoaPods/Xcodeproj/pull/853) 
 
+* file reference: Remove build files when underlying file_ref is removed.
+  [Ben Yohay](https://github.com/byohay)
+  [#861](https://github.com/CocoaPods/Xcodeproj/pull/861)
+
 ##### Bug Fixes
 
 * None.