Update local_cost.py

[amanpreet692]

Custom cost to be added for open scholar solver for the finetuned model: https://huggingface.co/akariasai/os_8b

"together_ai/meta-llama/Meta-Llama-3.1-8B-Instruct-Turbo": {
        "input_cost_per_token": 1.8e-07,
        "output_cost_per_token": 1.8e-07,
        "litellm_provider": "together_ai",
        "supports_function_calling": true,
        "supports_parallel_function_calling": true,
        "supports_response_schema": true,
        "mode": "chat",
        "supports_tool_choice": true
    }

-- sourced from littlm here: https://raw.githubusercontent.com/BerriAI/litellm/refs/heads/main/litellm/model_prices_and_context_window_backup.json

[mdarcy220]

lgtm and I think @regan-huff is still OOO for another week; idk if @dirkraft or anyone else understands the full mechanism for this right now, but it seems harmless to merge and can update if it turns out an additional change is needed