We had a nested spawn that was disguising the fact that the actual
`git_config` task was being dropped immediately instead of detached.
This only seems to cause problems in release builds due to timing
issues.

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:

- Fixed a bug where clicking the button to trust a git repository would
do nothing.