removed edits to whatsnew 0.21.0

Author: No-Stream

doc/source/whatsnew/v0.21.0.txt

@@ -130,7 +130,6 @@ Other Enhancements
 - `read_*` methods can now infer compression from non-string paths, such as ``pathlib.Path`` objects (:issue:`17206`).
 - :func:`pd.read_sas()` now recognizes much more of the most frequently used date (datetime) formats in SAS7BDAT files (:issue:`15871`).
 - :func:`DataFrame.items` and :func:`Series.items` is now present in both Python 2 and 3 and is lazy in all cases (:issue:`13918`, :issue:`17213`)
-- is_monotonic_increasing/decreasing is added to .groupby(). (:issue:`17015`)
 
 
 .. _whatsnew_0210.api_breaking: