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

Closes #58922

In #57973, a new timestamp format was introduced. For example, for a
commit from 13 months ago, the old formatter would output `"1 year
ago"`, whereas the new format outputs `"1 year, 1 month ago"`.

This new compound format is significantly longer than `"60 minutes
ago"`, which is currently used to calculate the maximum width of the
blame column here:

https://github.com/zed-industries/zed/blob/d989c7c5cdd057de2375a55bdc109ff61409801c/crates/editor/src/editor.rs#L11376-L11391

As a result, when a blame entry uses the `"{M} years, {N} months ago"`
format, its width exceeds the pre-calculated maximum, causing the text
to overlap with the line numbers.

This PR updates the placeholder string used for the maximum width
calculation to `"2 years, 11 months ago"`, ensuring the column is wide
enough to accommodate the longest possible compound timestamp.

Before:
<img width="1407" height="598" alt="before"
src="https://github.com/user-attachments/assets/f025f423-9ccc-432d-813c-4b861227a7a1"
/>

After:
<img width="1481" height="594" alt="after"
src="https://github.com/user-attachments/assets/c60cbd17-fdd4-471c-a4fc-3c2e7a3ccd5d"
/>

Release Notes:

- Fixed an issue where Git blame text would overlap with line numbers in
the gutter.