🧹 Fix false positive code health warning in executor.rs comment

[Tcode-Motion]

🎯 What: Rephrased the performance optimization comment block in runtime/vm/src/executor.rs to replace the exact code snippet self.frames.last_mut() with the plain English description "fetching the last mutable frame".

💡 Why: A code health automated process falsely flagged this documentation block as commented-out, unused code simply because it contained a syntactically correct code expression. Removing the block entirely (as might initially seem correct for dead code) would actively harm maintainability by deleting vital architectural documentation regarding optimization reasoning. Rephrasing it satisfies the heuristic scanner without losing context.

✅ Verification: Verified by successfully running the workspace testing suite (cargo test --workspace) and formatting check (cargo fmt --all -- --check), confirming that no functionality or formatting logic was broken.

✨ Result: The codebase retains its important documentation in a way that prevents automated false-positive warnings, improving overall code health reporting accuracy without degrading code comprehensibility.

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PR created automatically by Jules for task 7481590131010326152 started by @Tcode-Motion

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