Fix guidance for subclassing collections.Set()

Doc/library/collections.abc.rst

@@ -173,7 +173,7 @@ Notes on using :class:`Set` and :class:`MutableSet` as a mixin:
 
 (2)
    To override the comparisons (presumably for speed, as the
-   semantics are fixed), redefine :meth:`__le__` and
+   semantics are fixed), redefine :meth:`__le__` and :meth:`__ge__`,
    then the other operations will automatically follow suit.
 
 (3)

Lib/_collections_abc.py

@@ -183,7 +183,7 @@ class Set(Sized, Iterable, Container):
     methods except for __contains__, __iter__ and __len__.
 
     To override the comparisons (presumably for speed, as the
-    semantics are fixed), all you have to do is redefine __le__ and
+    semantics are fixed), redefine __le__ and __ge__,
     then the other operations will automatically follow suit.
     """