fix: silence pydantic warning about protected namespace

[cpacker]

@sarahwooders we probably want to change the fields to not start with model_, but this works for now

Based on instructions here: https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.protected_namespaces

Warning in reference in this:

$ memgpt server

/Users/loaner/Library/Caches/pypoetry/virtualenvs/pymemgpt-PCQPn4ce-py3.10/lib/python3.10/site-packages/pydantic/_internal/_fields.py:151: UserWarning: Field "model_endpoint_type" has conflict with protected namespace "model_".

You may be able to resolve this warning by setting `model_config['protected_namespaces'] = ()`.
  warnings.warn(
/Users/loaner/Library/Caches/pypoetry/virtualenvs/pymemgpt-PCQPn4ce-py3.10/lib/python3.10/site-packages/pydantic/_internal/_fields.py:151: UserWarning: Field "model_endpoint" has conflict with protected namespace "model_".

You may be able to resolve this warning by setting `model_config['protected_namespaces'] = ()`.
  warnings.warn(
/Users/loaner/Library/Caches/pypoetry/virtualenvs/pymemgpt-PCQPn4ce-py3.10/lib/python3.10/site-packages/pydantic/_internal/_fields.py:151: UserWarning: Field "model_wrapper" has conflict with protected namespace "model_".

You may be able to resolve this warning by setting `model_config['protected_namespaces'] = ()`.

[sarahwooders]

lgtm!