[fix] updated.check() type changed to Promise<boolean>

[chrskerr]

The current type for updated.check() is boolean which allows for subtle errors like the below. This will always be true since the runtime type for check() is a promise.

if (updated.check()) { // always true
   // do something
}

And the code should be:

if (await updated.check()) {
   // do something
}

Updating the types means that TS catches my mistake.

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[changeset-bot]

🦋 Changeset detected

Latest commit: dfc5e14

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

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Name	Status	Preview	Updated
kit	🔄 Building (Inspect)		Jan 9, 2023 at 0:42AM (UTC)

[dummdidumm]

Thank you!