🎨 Palette: Hide decorative FontAwesome icons from screen readers

[ErisonBarros]

💡 What: Added aria-hidden="true" to decorative FontAwesome tags in aula-2.md.
🎯 Why: GitBook often embeds textual fallbacks inside tags. This prevents screen readers from reading meaningless strings like ":map-marked-alt:".
♿ Accessibility: Improved screen reader experience by hiding purely decorative elements.

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PR created automatically by Jules for task 7549427646062108432 started by @ErisonBarros

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