improve changelog for latest changes

Author: bagerard

docs/changelog.rst

@@ -8,7 +8,7 @@ Development
 ===========
 - (Fill this out as you fix issues and develop your features).
 - Switch tox to use pytest instead of legacy `python setup.py test` #2804
-- improve ReferenceField wrong usage detection
+- Improve error reporting for wrong instantiation of ReferenceField
 - Fix no_dereference thread-safetyness #2830
 - BREAKING CHANGE: max_length in ListField is now keyword only on ListField signature
 - BREAKING CHANGE: Force `field` argument of ListField/DictField to be a field instance (e.g ListField(StringField()) instead of ListField(StringField)