remove whatsnew entry

Author: minggli

doc/source/whatsnew/v0.23.0.txt

@@ -295,7 +295,6 @@ Other Enhancements
 - ``IntervalIndex.astype`` now supports conversions between subtypes when passed an ``IntervalDtype`` (:issue:`19197`)
 - :class:`IntervalIndex` and its associated constructor methods (``from_arrays``, ``from_breaks``, ``from_tuples``) have gained a ``dtype`` parameter (:issue:`19262`)
 - Added :func:`SeriesGroupBy.is_monotonic_increasing` and :func:`SeriesGroupBy.is_monotonic_decreasing` (:issue:`17015`)
-- :func:`to_datetime` has gained ``require_iso8601`` parameter to mandate ISO8601-compliant datetime string conversion. (:issue:`19671`)
 - :func:`DataFrame.from_dict` now accepts a ``columns`` argument that can be used to specify the column names when ``orient='index'`` is used (:issue:`18529`)
 
 .. _whatsnew_0230.api_breaking: