bpo-43698: do not use `...` as argument name in docs (GH-30502)

(cherry picked from commit b9d8980d89bfaa4bf16d60f0488adcc9d2cbf5ef)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 9a9c87e..9523136 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -248,7 +248,7 @@
 
       class C:
           @classmethod
-          def f(cls, arg1, arg2, ...): ...
+          def f(cls, arg1, arg2): ...
 
    The ``@classmethod`` form is a function :term:`decorator` -- see
    :ref:`function` for details.