Update doc/source/whatsnew/v3.0.0.rst

Co-authored-by: Matthew Roeschke <[email protected]>

Author: matiaslindgren

doc/source/whatsnew/v3.0.0.rst

@@ -654,7 +654,7 @@ Groupby/resample/rolling
 
 Reshaping
 ^^^^^^^^^
-- :attr:`MultiIndex.names` containing ``None`` no longer throws ``AssertionError`` during join (:issue:`58721`)
+- Bug in :meth:`DataFrame.join` when a :class:`DataFrame` with a :class:`MultiIndex` would raise an ``AssertionError`` when :attr:`MultiIndex.names` contained ``None``. (:issue:`58721`)
 - Bug in :func:`qcut` where values at the quantile boundaries could be incorrectly assigned (:issue:`59355`)
 - Bug in :meth:`DataFrame.join` inconsistently setting result index name (:issue:`55815`)
 - Bug in :meth:`DataFrame.merge` where merging on a column containing only ``NaN`` values resulted in an out-of-bounds array access (:issue:`59421`)