fix(types): remove misleading betas TypedDict property for the Batch API

[RobertCraigie]

This is now a type error in the Batch API as the nested betas key won't actually do anything, you need to provide it at the top-level

client.beta.messages.batches.create(
    requests=[
        {
            "custom_id": "...",
            "params": {
                "model": "claude-3-sonnet-20240229",
                "messages": [],
                "max_tokens": 1024,
                "betas": [...],
            },
        }
    ]
)