`copy.__doc__` is out of date

Documentation

copy.__doc__ ends:

Classes can use the same interfaces to control copying that they use
to control pickling: they can define methods called __getinitargs__(),
__getstate__() and __setstate__().  See the documentation for module
"pickle" for information on these methods.

But __getinitargs__ went away with Python 2.

Linked PRs

• gh-138872

從 issue 中確定的 copy 模組 doc 文字開始，並將其最後一段與 Python 2 時代的參考資料進行比較。移除已過時的 getinitargs 參照，然後驗證產生的 copy 文件是否準確描述了其餘介面。