[issue45680] Documentation on `GenericAlias` objects and `__class_getitem__` could be improved

[miss-islington]

Change by miss-islington <mariatta.wijaya+miss-islington at gmail.com>:


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pull_requests: +27854
pull_request: https://github.com/python/cpython/pull/29619

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45680>
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