pythongh-131885: Document that dict.setdefault and dict.get take no keyword arguments (pythonGH-128208)

(cherry picked from commit edfbd8c)

Co-authored-by: Adam Dangoor <adamdangoor@gmail.com>

Author: adamtheturtle

Doc/library/stdtypes.rst

@@ -4577,7 +4577,7 @@ can be used interchangeably to index the same dictionary entry.
       such as an empty list.  To get distinct values, use a :ref:`dict
       comprehension <dict>` instead.
 
-   .. method:: get(key, default=None)
+   .. method:: get(key, default=None, /)
 
       Return the value for *key* if *key* is in the dictionary, else *default*.
       If *default* is not given, it defaults to ``None``, so that this method
@@ -4619,7 +4619,7 @@ can be used interchangeably to index the same dictionary entry.
 
       .. versionadded:: 3.8
 
-   .. method:: setdefault(key, default=None)
+   .. method:: setdefault(key, default=None, /)
 
       If *key* is in the dictionary, return its value.  If not, insert *key*
       with a value of *default* and return *default*.  *default* defaults to