format on save: javascript docs (#60070)

# Objective

JavaScript docs for default `format-on-save` settings are out of date.

Small docs followup to https://github.com/zed-industries/zed/pull/59710

## Solution

Change docs to say that JavaScript format-on-save is now off by default.

## 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 adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A
d7b9b28debChris Biscardi committed on 6/29/2026, 8:19:22 AM· committed by GitHubparent76e07d5
1 file changedLine totals unavailable