Do not require jiter to avoid dependency on Rust

[barracuda156]

Confirm this is a feature request for the Python library and not the underlying OpenAI API.

• This is a feature request for the Python library

Describe the feature or improvement you're requesting

Is it possible to make dependency on jiter optional? pydantic 1.x exists in rust-free version, and this project supports pydantic 1.9.x:

openai-python/pyproject.toml

Line 12 in 7193688

"pydantic>=1.9.0, <3",

It will be nice to avoid requiring Rust here.

Additional context

Rust is a very heavy dependency to build. Also, it is not supported on a number of non-mainstream platforms, where Python 3.x works fine.