Undeprecate the unload event

[ddbeck]

Summary

unload is marked as deprecated, but it doesn't satisfy the guidelines.

Test results and supporting details

• Mark unload as deprecated #21480 set the value in the first place, on the basis of Chrome's deprecation, not the spec.
• Clarify cases where we would fire the "unload" event, or maybe deprecate it? whatwg/html#6026 is still open, where the question of unload deprecation does not have consensus, much less specification text.
• Permission-Policy: unload mozilla/standards-positions#691 (comment) seems to indicate that the effort to deprecate this event has been abandoned (closed without a position being given by Mozilla or WebKit).

Given the evidence here, I think it's much too early to mark this event deprecated.

Related issues

n/a

[github-actions]

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