MX tests failing

[msaroufim]

Nightlies just started failing with a codegen error on _fp4_packed_to_bf16() on the latest pytorch nightlies

https://github.com/pytorch/ao/actions/runs/9638955431/job/26580435982?pr=427

@vkuzo for now I will pin nightlies to a specific version #428 since we're doing a branch cut on Monday and that might be too short to debug

[vkuzo]

thanks, looks like the triton pin got updated here (pytorch/pytorch#126098), I will take a look

[vkuzo]

#431