Update whats-new.rst (#217)

Author: malmans2

doc/whats-new.rst

@@ -6,7 +6,7 @@ What's New
 v0.5.2 (unreleased)
 ===================
 
-- Added :py:attr:`Dataset.cf.axes` to return a dictionary mapping valid keys to the variable names of their bounds. By `Mattia Almansi`_.
+- Added :py:attr:`Dataset.cf.bounds` to return a dictionary mapping valid keys to the variable names of their bounds. By `Mattia Almansi`_.
 - :py:meth:`DataArray.cf.differentiate` and :py:meth:`Dataset.cf.differentiate` can optionally correct
   sign of the derivative by interpreting the ``"positive"`` attribute. By `Deepak Cherian`_.