Updated release notes

docs/topics/release-notes.md

@@ -18,6 +18,7 @@ Major version numbers (x.0.0) are reserved for project milestones.  No major poi
 
 ### Master
 
+* Deprecate django.utils.simplejson in favor of Python 2.6's built-in json module.
 * Bugfix: Validation errors instead of exceptions when serializers receive incorrect types.
 * Bugfix: Validation errors instead of exceptions when related fields receive incorrect types.