Drop support of Python 3.7

[ericwb]

Confirm this is an issue with the Python library and not an underlying OpenAI API

• [X] This is an issue with the Python library

Describe the bug

Python 3.7 is already end-of-life as of 2023-06-27 as you see from the PSF here: https://devguide.python.org/versions/, yet this client is still supporting it.

I recommend dropping support as further fixes to the Python 3.7 runtime won't be made and could affect usage of this client.

To Reproduce

1. Go to https://devguide.python.org/versions/
2. Notice Python 3.7 end support as of 2023-06-27
3. Notice in https://github.com/openai/openai-python/blob/main/pyproject.toml#L24 this client still claims support.

Code snippets

n/a

OS

macOS

Python version

Python 3.7.x

Library version

openai v1.14.3

[rattrayalex]

Thanks @ericwb ! We do indeed plan to do this at the next major version.