Fix misuse of PyUnicode_GET_SIZE() => PyUnicode_GET_LENGTH()

And PyUnicode_GetSize() => PyUnicode_GetLength()
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 7438a70..a89798a 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -2941,7 +2941,7 @@
         PyErr_BadInternalCall();
         return NULL;
     }
-    llen = PyUnicode_GetSize(result);
+    llen = PyUnicode_GetLength(result);
     if (llen > INT_MAX) {
         PyErr_SetString(PyExc_ValueError,
                         "string too large in _PyBytes_FormatLong");