Update changelog

Author: liam923

CHANGES.md

@@ -6,6 +6,7 @@ unreleased
       (#1888)
     - `locate` can now disambiguate between files with identical names and contents
       (#1882)
+    - `occurrences` now reports stale files (#1885)
   + ocaml-index
     - Improve the granularity of index reading by segmenting the marshalization
       of the involved data-structures. (#1889)