ver 3.21.5

fix: Address multiple memory leaks in CodeBlock component (#4244)

* fix: address multiple memory leaks in CodeBlock component (CodeBlock_247, CodeBlock_459, CodeBlock_694)

* fix: Address review feedback for CodeBlock memory leak fixes

- Consolidate isMountedRef management into syntax highlighting useEffect
- Unify timeout cleanup patterns for consistent maintainability
- Maintain all existing memory leak protections
- Improve code organization and readability

Addresses review comments from daniel-lxs in PR #4244

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Co-authored-by: Daniel Riccio <ricciodaniel98@gmail.com>