Update simdutf Update simdutf to version 6.4.0, mostly to silence a newly-added clang warning that we're trying to enable. The new files were obtained from singleheader.zip here: https://github.com/simdutf/simdutf/releases/tag/v6.4.0 BYPASS_LARGE_CHANGE_WARNING: third-party update Bug: 403236787 No-Presubmit: true Low-Coverage-Reason: OTHER Change-Id: I4b66617efd83c833a9f86f8895002ccafba8a47d Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6386726 Reviewed-by: Nidhi Jaju <[email protected]> Commit-Queue: Devon Loehr <[email protected]> Cr-Commit-Position: refs/heads/main@{#1438111} NOKEYCHECK=True GitOrigin-RevId: df979a41dac69c24bcb96f3a164154d05ac5e682