`copy.__doc__` is out of date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

从 issue 中确定的 copy 模块 doc 文本开始，并将其最后一段与 Python 2 时代的参考资料进行比较。删除已过时的 getinitargs 引用，然后验证生成的 copy 文档是否准确描述了其余接口。