[3.13] Docs: Fix specifications of gcvisitobjects_t (pythonGH-132433) (python#132441)

Docs: Fix specifications of `gcvisitobjects_t` (pythonGH-132433)

`gcvisitobjects_t` callbacks should return 1 for the iteration to continue instead of 0.
(cherry picked from commit 1e5798e)

Co-authored-by: da-woods <[email protected]>

Author: miss-islington

Doc/c-api/gcsupport.rst

@@ -277,7 +277,7 @@ the garbage collector.
 
    Type of the visitor function to be passed to :c:func:`PyUnstable_GC_VisitObjects`.
    *arg* is the same as the *arg* passed to ``PyUnstable_GC_VisitObjects``.
-   Return ``0`` to continue iteration, return ``1`` to stop iteration. Other return
+   Return ``1`` to continue iteration, return ``0`` to stop iteration. Other return
    values are reserved for now so behavior on returning anything else is undefined.
 
    .. versionadded:: 3.12