gh-101100: fix sphinx warnings in library/signal.rst

[LamentXU123]

signal.rst:270: WARNING: c:func reference target not found: signal [ref.func]
signal.rst:668: WARNING: py:attr reference target not found: si_signo [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_code [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_errno [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_pid [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_uid [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_status [ref.attr]
signal.rst:668: WARNING: py:attr reference target not found: si_band [ref.attr]

• The c:func referrence in line 270 was suppressed
• In line 668, the py:attr references were namely the attr of siginfo_t structure. In library os we also mentioned this structure in function waitid:

   The return value is an object representing the data contained in the
   :c:type:`siginfo_t` structure with the following attributes:

   * :attr:`!si_pid` (process ID)
   * :attr:`!si_uid` (real user ID of the child)
   * :attr:`!si_signo` (always :const:`~signal.SIGCHLD`)
   * :attr:`!si_status` (the exit status or signal number, depending on :attr:`!si_code`)
   * :attr:`!si_code` (see :data:`CLD_EXITED` for possible values)

So I just suppress all of them, similar to how we did in os.rst

• Issue: Fix all Sphinx reference warnings in the documentation #101100

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📚 Documentation preview 📚: https://cpython-previews--139930.org.readthedocs.build/

[ZeroIntensity]

! syntax should be reserved for actual Python APIs that we haven't documented, not for Unix APIs that aren't part of Python at all. Please make these an inline codeblock instead.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[LamentXU123]

I have made the requested changes; please review again

Should I add these changes to document of os either?

[bedevere-app]

Thanks for making the requested changes!

@ZeroIntensity: please review the changes made to this pull request.

[miss-islington-app]

Thanks @LamentXU123 for the PR, and @ZeroIntensity for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-app]

GH-139966 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-139967 is a backport of this pull request to the 3.13 branch.