docs(headless popover): fix examples styles to make them easier to understand

[maiieul]

What is it?

• [ ] Feature / enhancement
• [ ] Bug
• [x] Docs / tests
• [ ] Other

Why is it needed?

The previous styles were kinda broken 😅

Checklist:

• [ ] My code follows the developer guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have ran pnpm change and documented my changes
• [ ] I have add necessary docs (if needed)
• [ ] Added new tests to cover the fix / functionality

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: cdaeed6fd6a8f2b25c5d3c263077068f82eefd21

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

This PR includes changesets to release 1 package

| Name | Type | | --------------- | ----- | | @qwik-ui/styled | Patch |

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