Fix useId mismatch due to top level Fragments

[marvinhagemeister]

With preactjs/preact#3758 we need to include Fragments when setting masks. But core has an optimization where we flatten a Fragment when it's the top level node of the return value of a component.

function Foo() {
  // Will be flattened
  return <Fragment>...</Fragment>
}

[changeset-bot]

🦋 Changeset detected

Latest commit: 9ec2dc9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
preact-render-to-string	Patch

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