Refer to concat in root namespace

Author: neinkeinkaffee

doc/source/whatsnew/v1.4.0.rst

@@ -444,15 +444,15 @@ Deprecated Frame.append and Series.append
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 :meth:`DataFrame.append` and :meth:`Series.append` have been deprecated and will be removed in Pandas 2.0.
-Use :func:`pandas.core.reshape.concat` instead (:issue:`35407`).
+Use :func:`pandas.concat` instead (:issue:`35407`).
 
 *Deprecated syntax*
 
 .. code-block:: ipython
 
     In [1]: pd.Series([1, 2]).append(pd.Series([3, 4])
     Out [1]:
-    <stdin>:1: FutureWarning: The frame.append method is deprecated and will be removed from pandas in a future version. Use pandas.core.reshape.concat instead.
+    <stdin>:1: FutureWarning: The frame.append method is deprecated and will be removed from pandas in a future version. Use pandas.concat instead.
     0    1
     1    2
     0    3