bpo-35295: Remove outdated comment. (GH-24453)

(cherry picked from commit d938816)

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

Author: miss-islington

Include/cpython/unicodeobject.h

@@ -760,13 +760,6 @@ PyAPI_FUNC(const char *) PyUnicode_AsUTF8AndSize(
 
    Use of this API is DEPRECATED since no size information can be
    extracted from the returned data.
-
-   *** This API is for interpreter INTERNAL USE ONLY and will likely
-   *** be removed or changed for Python 3.1.
-
-   *** If you need to access the Unicode object as UTF-8 bytes string,
-   *** please use PyUnicode_AsUTF8String() instead.
-
 */
 
 PyAPI_FUNC(const char *) PyUnicode_AsUTF8(PyObject *unicode);