Fix typo in RadioGroup docs

[rezrah]

Summary

Fixes a typo in one of the radio group docs examples.

Contributor checklist:

• [ ] All new and existing CI checks pass
• [ ] Tests prove that the feature works and covers both happy and unhappy paths
• [ ] Any drop in coverage, breaking changes or regressions have been documented above
• [ ] UI Changes contain new visual snapshots (generated by adding update snapshots label to the PR)
• [ ] All developer debugging and non-functional logging has been removed
• [ ] Related issues have been referenced in the PR description

Reviewer checklist:

• [ ] Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• [ ] Check that tests prove the feature works and covers both happy and unhappy paths
• [ ] Check that there aren't other open Pull Requests for the same update/change

Screenshots:

N/A see diffs

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: cb29c3e0ea9d1f115f793e4140f7f3573b94c47d

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[github-actions[bot]]

🟢 No design token changes found

[github-actions[bot]]

⚠️ Visual differences found

Our visual comparison tests found UI differences.

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