chore(9.x): release 9.1.0

[github-actions[bot]]

:robot: I have created a release beep boop

9.1.0 (2023-06-13)

Features

• emit warning for req.closed only once (86cab8c)

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[github-actions[bot]]

:robot: Release is at https://github.com/restify/node-restify/releases/tag/v9.1.0 :sunflower: