docs(changelog): add note about closing #4674

closes #4674

CHANGELOG.md

@@ -1,3 +1,8 @@
+# 3.2.0-pre (unreleased)
+
+### Enhancements
+* **Login**: Adds option to disable username/password logins, closes [#4674](https://github.com/grafana/grafana/issues/4674)
+
 # 3.1.0-beta1 (2016-06-23)
 
 ### Enhancements