add brief whatsnew

Author: jorisvandenbossche

doc/source/whatsnew/v3.0.0.rst

@@ -749,6 +749,10 @@ Other API changes
 - :meth:`ExtensionDtype.construct_array_type` is now a regular method instead of a ``classmethod`` (:issue:`58663`)
 - Comparison operations between :class:`Index` and :class:`Series` now consistently return :class:`Series` regardless of which object is on the left or right (:issue:`36759`)
 - Numpy functions like ``np.isinf`` that return a bool dtype when called on a :class:`Index` object now return a bool-dtype :class:`Index` instead of ``np.ndarray`` (:issue:`52676`)
+- Methods that can operate in-place (:meth:`~DataFrame.replace`, :meth:`~DataFrame.fillna`,
+  :meth:`~DataFrame.ffill`, :meth:`~DataFrame.bfill`, :meth:`~DataFrame.interpolate`,
+  :meth:`~DataFrame.where`, :meth:`~DataFrame.mask`, :meth:`~DataFrame.clip`) now return
+  the modified DataFrame or Series (``self``) instead of ``None`` when ``inplace=True`` (:issue:`63207`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.deprecations: