ui: Use VersionControl colors for added and removed diff stats (#64083)

# Objective
Fixes #63806 
Diff stats use general `success` and `error` colors for added and
deleted line counts.

## Solution

Using `version_control.added` and `version_control.deleted` instead to
match the version control icons color palette.

## Testing

- Did you test these changes? If so, how?
built and ran locally.


- Are there any parts that need more testing?
no
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
no
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?

## 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

## Showcase

<details>
  <summary>Click to view showcase</summary>

<img width="2394" height="776" alt="zed_diff_stat_colors"
src="https://github.com/user-attachments/assets/5c3f89fd-4a07-4fc8-83f9-5f6e133dfe86"
/>
Left Zed - unchanged
Right Zed - fixed

</details>

---

Release Notes:

- Fixed diff statistics to use the theme’s version-control colors for
added and deleted line counts.

crates/ui/src/components/diff_stat.rs

@@ -44,12 +44,12 @@ impl RenderOnce for DiffStat {
             .gap_1()
             .child(
                 Label::new(format!("+\u{2009}{added}"))
-                    .color(Color::Success)
+                    .color(Color::VersionControlAdded)
                     .size(self.label_size),
             )
             .child(
                 Label::new(format!("\u{2012}\u{2009}{removed}"))
-                    .color(Color::Error)
+                    .color(Color::VersionControlDeleted)
                     .size(self.label_size),
             )
             .when_some(tooltip, |this, tooltip| {