Doc that 'sorted' args are keyword-only, fix 'reverse' default (#2706)

Doc/library/functions.rst

@@ -1361,7 +1361,7 @@ are always available.  They are listed here in alphabetical order.
    :func:`itertools.islice` for an alternate version that returns an iterator.
 
 
-.. function:: sorted(iterable[, key][, reverse])
+.. function:: sorted(iterable, *, key=None, reverse=False)
 
    Return a new sorted list from the items in *iterable*.
 

Doc/library/stdtypes.rst

@@ -1161,7 +1161,7 @@ application).
    :ref:`mutable <typesseq-mutable>` sequence operations. Lists also provide the
    following additional method:
 
-   .. method:: list.sort(*, key=None, reverse=None)
+   .. method:: list.sort(*, key=None, reverse=False)
 
       This method sorts the list in place, using only ``<`` comparisons
       between items. Exceptions are not suppressed - if any comparison operations