``ndarray``, ``dtype`` and ``number`` are now runtime-subscriptable
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Mimicking :pep:`585`, the `~numpy.ndarray`, `~numpy.dtype` and `~numpy.number`
classes are now subscriptable for python 3.9 and later.
Consequently, expressions that were previously only allowed in .pyi stub files
or with the help of ``from __future__ import annotations`` are now also legal
during runtime.

.. code-block:: python

    >>> import numpy as np
    >>> from typing import Any

    >>> np.ndarray[Any, np.dtype[np.float64]]
    numpy.ndarray[typing.Any, numpy.dtype[numpy.float64]]

Add a release note for `__class_getitem__`
DOC: Add a release note for `__class_getitem__`
