It seems their verification got stricter, at least stricter than
Anthropics. Only set the output config if we have an effort.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #54036

Release Notes:

- copilot_chat: Fix invalid reasoning effort for some models.

Co-authored-by: John Tur <john-tur@outlook.com>