What?

This PR translates the React Compiler notes in the following files:

• src/content/reference/react/useCallback.md
• src/content/reference/react/useMemo.md

Why?

These sections were missing Portuguese (Brazil) translation. This completes the translation for the React Compiler documentation notes in both hooks.

How?

Translated the <Note> blocks about React Compiler while keeping:

• Technical terms in English (React Compiler, useCallback, useMemo)
• Code examples unchanged
• Markdown formatting intact