Replace :func: by :cfunc:

To get links to the C functions
diff --git a/Doc/c-api/bytes.rst b/Doc/c-api/bytes.rst
index b66047b..c1a82b2 100644
--- a/Doc/c-api/bytes.rst
+++ b/Doc/c-api/bytes.rst
@@ -114,7 +114,7 @@
 
 .. cfunction:: PyObject* PyBytes_FromFormatV(const char *format, va_list vargs)
 
-   Identical to :func:`PyBytes_FromFormat` except that it takes exactly two
+   Identical to :cfunc:`PyBytes_FromFormat` except that it takes exactly two
    arguments.