Update changelog.md

Author: janmeier

changelog.md

@@ -1,6 +1,7 @@
 # Next
 - [INTERNALS] Update `inflection` dependency to v1.5.3
 - [FEATURE] Replaced string error messages for connection errors with error objects. [#2576](https://github.com/sequelize/sequelize/pull/2576)
+- [FEATURE] Support for updating fields on duplicate key in bulk update (mysql only) [#2692](https://github.com/sequelize/sequelize/pull/2692)
 
 #### Backwards compatability changes
 - Some of the string error messages for connection errors have been replaced with actual error instances. Checking for connection errors should now be more consistent.