refactor(allocator): remove unnecessary Send impl for FixedSizeAllocator

[overlookmotel]

Pure refactor. #12380 removed the NonNull<u8> from FixedSizeAllocator, so FixedSizeAllocator is now automatically Send. Remove redundant manual Send impl.

[overlookmotel]

• refactor(allocator): remove unnecessary Send impl for FixedSizeAllocator #12426 👈 (View in Graphite)
• refactor(napi/oxlint): simplify atomic operations #12425
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #12426 will not alter performance

_{Comparing 07-20-refactor_allocator_remove_unnecessary_send_impl_for_fixedsizeallocator_ (124d376) with main (10fe5f2)}

Summary

✅ 34 untouched benchmarks

[overlookmotel]

Merge activity

• Jul 21, 2:24 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Jul 21, 2:24 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Jul 21, 2:47 PM UTC: Merged by the Graphite merge queue.