gh-105927: PyWeakref_GetRef() returns 1 on success

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PyWeakref_GetRef() now returns 1 on success, and return 0 if the reference is dead.

• Issue: C API: Add PyWeakref_GetRef() function #105927

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📚 Documentation preview 📚: https://cpython-previews--106561.org.readthedocs.build/

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PR to update the newly added C API to respect the new C API guidelines: https://devguide.python.org/developer-workflow/c-api/index.html

APIs with lesser and greater results must return 0 for the lesser result, and 1 for the greater result. Consider a lookup function with a three-way return: (...)

cc @erlend-aasland

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cc @encukou

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Thanks for the review @serhiy-storchaka.

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I updated pythoncapi-compat: python/pythoncapi-compat@d000b55