Upgrade/Install: Align update details toggle line height

[aldorizona10-glitch]

Summary

Sets the update-details toggle button to inherit the notice paragraph line height. This keeps the disclosure icon aligned with the message text and removes the one-pixel vertical discrepancy described in the ticket.

Trac ticket: https://core.trac.wordpress.org/ticket/64588

Testing

• git diff --check
• Verified the patch applies cleanly in reverse against the current checkout.

This pull request is for code review. Core changes are committed through the WordPress SVN workflow.

[github-actions]

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Props aldorza.

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[github-actions]

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