Add missing note to __lt__

Author: asmeurer

src/array_api_stubs/_draft/array_object.py

@@ -829,6 +829,9 @@ def __lt__(self: array, other: Union[int, float, array], /) -> array:
 
         .. note::
            Element-wise results must equal the results returned by the equivalent element-wise function :func:`~array_api.less`.
+
+        .. note::
+           Comparison of arrays without a corresponding promotable data type (see :ref:`type-promotion`) is undefined and thus implementation-dependent.
         """
 
     def __matmul__(self: array, other: array, /) -> array: