fixed #6801: symmetric_difference_update also accepts pipe

Doc/library/stdtypes.rst

@@ -1787,7 +1787,7 @@ The constructors for both classes work the same:
          Accepts multiple input iterables.
 
    .. method:: symmetric_difference_update(other)
-               set ^= other
+               set ^= other | ...
 
       Update the set, keeping only elements found in either set, but not in both.
 

Misc/NEWS

@@ -1229,6 +1229,9 @@ Documentation
 - Issue #6556: Fixed the Distutils configuration files location explanation
   for Windows.
 
+- Issue #6801 : symmetric_difference_update also accepts |.
+  Thanks to Carl Chenet. 
+
 C-API
 -----