Use more PEP 570 syntax in the documentation. (GH-13720)

diff --git a/Doc/faq/programming.rst b/Doc/faq/programming.rst
index 9660a70..a00c6a0 100644
--- a/Doc/faq/programming.rst
+++ b/Doc/faq/programming.rst
@@ -554,8 +554,8 @@
 5) Or bundle up values in a class instance::
 
       class callByRef:
-          def __init__(self, **args):
-              for (key, value) in args.items():
+          def __init__(self, /, **args):
+              for key, value in args.items():
                   setattr(self, key, value)
 
       def func4(args):