verbose changelog

Author: dakshvar22

CHANGELOG.rst

@@ -23,6 +23,8 @@ This project adheres to `Semantic Versioning`_ starting with version 1.0.
 Bugfixes
 --------
 - `#5505 <https://github.com/rasahq/rasa/issues/5505>`_: Set default value for ``weight_sparsity`` in ``ResponseSelector`` to ``0``.
+    This fixes a bug in the default behaviour of ``ResponseSelector`` which was accidentally introduced in ``rasa==1.8.0``.
+    Users should update to this version and re-train their models if ``ResponseSelector`` was part of their pipeline.
 
 
 [1.9.2] - 2020-03-26