Log Message:
dav1d: update to 1.4.0.

Changes for 1.4.0 'Road Runner':
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1.4.0 is a medium release of dav1d, focusing on new architecture support and \ 
optimizations

- AVX-512 optimizations for z1, z2, z3 in 8bit and high-bitdepth
- New architecture supported: loongarch
- Loongarch optimizations for 8bit
- New architecture supported: RISC-V
- RISC-V optimizations for itx
- Misc improvements in threading and in reducing binary size
- Fix potential integer overflow with extremely large frame sizes