[three] Fix isType properties

[Methuselah96]

Fixes a bug in #74890, ported from three-types/three-ts-types#2129

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• Test the change in your own code. (Compile and run.)
• Add or edit tests to reflect the change.
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• Avoid common mistakes.
• Run pnpm test <package to test>.

If changing an existing definition:

• Provide a URL to documentation or source code which provides context for the suggested changes: [three] Revert static is(Vector|Matrix*) changes. three-types/three-ts-types#2129
• If this PR brings the type definitions up to date with a new version of the JS library, update the version number in the package.json.

[typescript-bot]

@Methuselah96 Thank you for submitting this PR!

This is a live comment that I will keep updated.

1 package in this PR

• three — on npm, on unpkg (author is owner)

Code Reviews

Because this is a widely-used package, a DT maintainer will need to review it before it can be merged.

You can test the changes of this PR in the Playground.

Status

• ✅ No merge conflicts
• ✅ Continuous integration tests have passed
• 🕐 Most recent commit is approved by a DT maintainer

Once every item on this list is checked, I'll ask you for permission to merge and publish the changes.

---

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[typescript-bot]

🔔 @joshuaellis — please review this PR in the next few days. Be sure to explicitly select Approve or Request Changes in the GitHub UI so I know what's going on.