Update what's new

Author: mgunyho

doc/whats-new.rst

@@ -51,6 +51,8 @@ Bug fixes
   By `Oliver Lopez <https://github.com/lopezvoliver>`_.
 - Fix bug where index variables would be changed inplace (:issue:`6931`, :pull:`6938`)
   By `Michael Niklas <https://github.com/headtr1ck>`_.
+- Fix step plots with ``hue`` arg. (:pull:`6944`)
+  By `András Gunyhó <https://github.com/mgunyho>`_.
 
 Documentation
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