Clean up the dtrace code and documentation for the hook is not using

[Zheaoli]

Bug report

Bug description:

8 years ago, @ambv add dtrace support in CPython in https://github.com/python/cpython/commit/a785c87d6eacbed81543a8afe3cb098fabb9610a

For now, after check the code, I think the point following below is not used in CPython code

• [ ] function__entry
• [ ] function__return
• [ ] instance__new__start
• [ ] instance__new__done
• [ ] instance__delete__start
• [ ] instance__delete__done
• [ ] line

I think we need to clean up the code and the document in https://docs.python.org/3/howto/instrumentation.html

cc @markshannon

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux