DOC: Update CHANGES.txt

Author: Prabhu-LANL

CHANGES.txt

@@ -9,6 +9,9 @@ NOTE: 4.3.0 now requires Python 3.6.0 and above. Python 3.5.x is no longer suppo
 
 RELEASE  VERSION/DATE TO BE FILLED IN LATER
 
+  From Prabhu S. Khalsa:
+    - Fix typo in user documentation (issue #4458)
+
   From Ataf Fazledin Ahamed:
     - Use of NotImplemented instead of NotImplementedError for special methods
       of _ListVariable class