Update v1.4.0.rst

Author: AlexeyGy

doc/source/whatsnew/v1.4.0.rst

@@ -108,6 +108,7 @@ Other enhancements
 - Methods that relied on hashmap based algos such as :meth:`DataFrameGroupBy.value_counts`, :meth:`DataFrameGroupBy.count` and :func:`factorize` ignored imaginary component for complex numbers (:issue:`17927`)
 - Add :meth:`Series.str.removeprefix` and :meth:`Series.str.removesuffix` introduced in Python 3.9 to remove pre-/suffixes from string-type :class:`Series` (:issue:`36944`)
 - :meth:`.GroupBy.mean` now supports ``NaT`` values (:issue:`43132`)
+-
 
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