Fix Unicode doc and replace use of macro with PyMem_New function (GH-94088)

Author: pamelafox

Doc/c-api/unicode.rst

@@ -819,7 +819,7 @@ wchar_t Support
    most C functions. If *size* is ``NULL`` and the :c:type:`wchar_t*` string
    contains null characters a :exc:`ValueError` is raised.
 
-   Returns a buffer allocated by :c:func:`PyMem_Alloc` (use
+   Returns a buffer allocated by :c:func:`PyMem_New` (use
    :c:func:`PyMem_Free` to free it) on success. On error, returns ``NULL``
    and *\*size* is undefined. Raises a :exc:`MemoryError` if memory allocation
    is failed.

Objects/unicodeobject.c

@@ -2843,7 +2843,7 @@ PyUnicode_AsWideCharString(PyObject *unicode,
     }
 
     buflen = unicode_get_widechar_size(unicode);
-    buffer = (wchar_t *) PyMem_NEW(wchar_t, (buflen + 1));
+    buffer = (wchar_t *) PyMem_New(wchar_t, (buflen + 1));
     if (buffer == NULL) {
         PyErr_NoMemory();
         return NULL;