bpo-37122: Make co->co_argcount represent the total number of positonal arguments in the code object (GH-13726)

diff --git a/Doc/c-api/code.rst b/Doc/c-api/code.rst
index 7aa91ee..92baa4c 100644
--- a/Doc/c-api/code.rst
+++ b/Doc/c-api/code.rst
@@ -42,6 +42,8 @@
 
    .. versionchanged:: 3.8
       An extra parameter is required (*posonlyargcount*) to support :PEP:`570`.
+      The first parameter (*argcount*) now represents the total number of positional arguments,
+      including positional-only.
 
    .. audit-event:: code.__new__ "code filename name argcount kwonlyargcount nlocals stacksize flags"