GenericPromise::all() won't compile as it's not setup to handle `Expected<void, T>` type.
<rdar://problem/117837167>
Pull request: https://github.com/WebKit/WebKit/pull/19935
*** Bug 264122 has been marked as a duplicate of this bug. ***
Committed 270344@main (cc6dee38764b): <https://commits.webkit.org/270344@main> Reviewed commits have been landed. Closing PR #19935 and removing active labels.