Ambiguous docs around fork deletion can lead to confusion

[ahpook]

Code of Conduct

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What article on docs.github.com is affected?

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/what-happens-to-forks-when-a-repository-is-deleted-or-changes-visibility#deleting-a-public-repository

What part(s) of the article would you like to see updated?

The text of the linked section on deleting a fork says only that "a fork" will be promoted to be the head of a fork network when the current upstream is deleted. This can lead to confusion about the expected behavior in this scenario. In fact, the current oldest fork will be promoted to the new upstream, and a simple change to the docs could eliminate that ambiguity and subsequent confusion.

Additional information

A security researcher was confused about this behavior and posted that when the head of a fork network is deleted, and arbitrary fork is promoted to be the head of the network, which could introduce a takeover attack if the fork thus promoted was owned by a bad actor. Clearly documenting that it's the oldest active fork rather than an arbitrary one would reduce the frightening possibility of a takeover.

https://x.com/trufflesec/status/1823069323348611345

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[nguyenalex836]

@ahpook Thank you for opening an issue and linking it to your PR! ✨