Safety comment isn't actually a safety requirement

[comex]

I admit this issue is a real nitpick. But src/arena/release.rs contains:

/// # Safety
///
/// **Do not** push objects into the arena that require destructors.
/// Destructors are not executed. Use a pool allocator for that.

This isn't actually a safety requirement in the Rust sense, only a correctness requirement. Skipping destructors is not considered unsafe (except when Pin is involved). So this shouldn't be listed under Safety.