[docs] [issue33921] Explain that '' can be used to bind to all interfaces for the AF_INET address family in the docs

[Ned Deily]

Ned Deily <nad at python.org> added the comment:

John, since you raised the issue, would you like to provide a doc PR?

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keywords: +easy
nosy: +ned.deily
stage:  -> needs patch
versions:  -Python 3.5

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