remove doc note

Author: jreback

doc/source/whatsnew/v0.24.0.txt

@@ -124,7 +124,6 @@ Datetimelike API Changes
 ExtensionType Changes
 ^^^^^^^^^^^^^^^^^^^^^
 
-- ``ExtensionArray`` has gained the abstract methods ``.dropna()`` and ``.append()`` (:issue:`21185`)
 - ``ExtensionDtype`` has gained the ability to instantiate from string dtypes, e.g. ``decimal`` would instantiate a registered ``DecimalDtype``; furthermore
   the ``ExtensionDtype`` has gained the method ``construct_array_type`` (:issue:`21185`)
 - The ``ExtensionArray`` constructor, ``_from_sequence`` now take the keyword arg ``copy=False`` (:issue:`21185`)