add description for bugfix in whatsnew

Author: annika-rudolph

doc/source/whatsnew/v3.0.0.rst

@@ -409,7 +409,7 @@ Missing
 MultiIndex
 ^^^^^^^^^^
 - :func:`DataFrame.loc` with ``axis=0``  and :class:`MultiIndex` when setting a value adds extra columns (:issue:`58116`)
--
+- :func:`MultiIndex.get_level_values` accessing a :class:`DatetimeIndex` does not carry the frequency attribute along (:issue:`58327`, :issue:`57949`)
 
 I/O
 ^^^