Remove OpenAI referenece in git command endpoint

What does this MR do and why?

A clean-up task for removing OpenAI references within our code base. We've removed the OpenAI client from performing requests with the following issue. This is just a small description change.

https://gitlab.com/gitlab-org/gitlab/-/issues/432549

Remove OpenAI referenece in git command endpoint

The following work is related towards our OpenAI clean up.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

This is only a name change. There is no source code change outside of string comment.