Lines 46-61 in infra_utils.py fails for Llama models

[r-gould]

Line 46 of lit/utils/infra_utils.py splits text with "[INST]" which is only present in the Mistral chat template (resulting in line 47 throwing an error for non-Mistral models), and line 49 similarly for "<｜User｜>" which is only present for DeepSeek models. Should lines 46-48 and lines 49-61 each be wrapped in if blocks?

[aypan17]

Yeah, I think there's not a really clean way to fix it other than having if blocks. Feel free to make a PR if you want!