docs: Improve image display aspect ratio (#52511)

## Context

Updates the image heights to auto on the docs pages, so that they don't
get squishy and keep their correct aspect ratio.

## 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)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A
260280d3e7Gaauwe Rombouts committed on 3/26/2026, 4:21:41 PM· committed by GitHubparentdd0d87f
2 files changedLine totals unavailable