Fix the documentation for set.copy() (GH-12176)

Remove 's' mention as there's no argument.
(cherry picked from commit e942e7b5)
Co-authored-by: Andre Delfino <adelfino@gmail.com>

Doc/library/stdtypes.rst

@@ -1909,7 +1909,7 @@ The constructors for both classes work the same:
 
    .. method:: copy()
 
-      Return a new set with a shallow copy of *s*.
+      Return a shallow copy of the set.
 
 
    Note, the non-operator versions of :meth:`union`, :meth:`intersection`,