Add change to whats-new.rst

Author: tomvothecoder

doc/whats-new.rst

@@ -31,7 +31,7 @@ Breaking changes
 Deprecations
 ~~~~~~~~~~~~
 - The `dt.weekday_name` parameter wasn't functional on modern pandas versions and has been removed. (:issue:`8610`, :pull:`8664`)
-  By `Sam Coleman <https://github.com/nameloCmaS>`_.
+  By `Sam Coleman <https://github.com/nameloCmaS>`_. 
 
 
 Bug fixes
@@ -40,7 +40,9 @@ Bug fixes
 
 Documentation
 ~~~~~~~~~~~~~
-
+- Fix `variables` arg typo in `Dataset.sortby()` docstring
+ (:issue:`8663`, :pull:`8670`)
+  By `Sam Coleman <https://github.com/nameloCmaS>`_.  
 
 Internal Changes
 ~~~~~~~~~~~~~~~~