DOC: add Performance improvement bullet for LineCollection speed-up

Author: EvMossan

doc/source/whatsnew/v3.0.0.rst

@@ -667,6 +667,7 @@ Performance improvements
 - Performance improvement in ``DataFrameGroupBy.__len__`` and ``SeriesGroupBy.__len__`` (:issue:`57595`)
 - Performance improvement in indexing operations for string dtypes (:issue:`56997`)
 - Performance improvement in unary methods on a :class:`RangeIndex` returning a :class:`RangeIndex` instead of a :class:`Index` when possible. (:issue:`57825`)
+- Performance improvement in ``DataFrame.plot(kind="line")``: very wide DataFrames (more than 200 columns) are now rendered with a single :class:`matplotlib.collections.LineCollection` instead of one ``Line2D`` per column, reducing draw time by roughly 7 × on a 2000-column frame. (:issue:`61532`, :pr:`61764`)
 
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 .. _whatsnew_300.bug_fixes: