OSV-2021-1748 Heap-buffer-overflow in jxl::N_AVX2::FloatToRGBA8

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=42839 Crash type: Heap-buffer-overflow WRITE 1 Crash state: jxl::NAVX2::FloatToRGBA8 jxl::FinalizeImageRect jxl::ThreadPool::RunCallStatejxl::FinalizeFrameDecoding...