Patch release v4.51.1

Since the release of Llama 4, we have fixed a few issues that we are now releasing in patch v4.51.1

• Fixing flex attention for torch=2.6.0 (#37285)
• more fixes for post-training llama4 (#37329)
• Remove HQQ from caching allocator warmup (#37347)
• fix derived berts _init_weights (#37341)
• Fix init empty weights without accelerate (#37337)
• Fix deepspeed with quantization (#37324)
• fix llama4 training (#37319)
• fix flex attn when optional args aren't passed (#37327)
• Multiple llama4 fixe (#37353)

Thanks all for your patience