CLN: Remove versionadded in groupby.rst (#22503)

gfyoung · jreback · commit d2b847f75d95 · 2018-08-28T08:04:46.000-04:00
Follow-up to gh-22415.
diff --git a/doc/source/groupby.rst b/doc/source/groupby.rst
@@ -103,8 +103,6 @@ consider the following ``DataFrame``:
 
 .. note::
 
-   .. versionadded:: 0.20
-
    A string passed to ``groupby`` may refer to either a column or an index level.
    If a string matches both a column name and an index level name, a
    ``ValueError`` will be raised.
