Update whatsnew/v3.0.0.rst

Author: hombit

doc/source/whatsnew/v3.0.0.rst

@@ -466,6 +466,7 @@ Sparse
 ExtensionArray
 ^^^^^^^^^^^^^^
 - Bug in :meth:`api.types.is_datetime64_any_dtype` where a custom :class:`ExtensionDtype` would return ``False`` for array-likes (:issue:`57055`)
+- Bug in :meth:`core.arrays.ExtensionArray.__setitem__` which caused wrong behaviour when using an integer array with repeated values as a key (:issue:`58530`)
 
 Styler
 ^^^^^^