fix syntax highlight in modernjs.mdx

[NookieGrey]

Description

For some reason syntax in the last code example wasn't correct highlighted. This PR fixes that problem.

Types of changes

• Docs change

Checklist

• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the documentation.

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⚠️ No Changeset found

Latest commit: c3ce29e

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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