Bash listed `fish` in `modeline_aliases`, so a `filetype=fish` modeline
resolved to Shell Script before the real [Fish
language](https://zed.dev/extensions/fish) could match by name or
grammar. Fish is intentionally non-POSIX, so the Bash grammar is the
wrong fit here.

| Header | After |
|--------|--------|
| <img width="1912" height="1237" alt="image"
src="https://github.com/user-attachments/assets/ed212a24-92aa-4ede-a432-47c6c6724f08"
/> | <img width="1732" height="1125" alt="image"
src="https://github.com/user-attachments/assets/934140b3-9473-4cca-a3e5-84aa3c4d827a"
/> |

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] 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
- [ ] Performance impact has been considered and is acceptable

Closes #58532.

Release Notes:

- Dropped `fish` from `modeline_aliases` which forced the file to be
detected as Shell Script instead of Fish