Swap TransparentUi to use a stable sort (#9598)

# Objective

- Fix the `borders`, `ui` and `text_wrap_debug` examples.

## Solution

- Swap `TransparentUi` to use a stable sort

---

This is the smallest change to fix the examples but ideally this is
fixed by setting better sort keys for the UI elements such that we can
swap back to an unstable sort.

crates/bevy_ui/src/render/render_pass.rs

@@ -112,6 +112,11 @@ impl PhaseItem for TransparentUi {
         self.draw_function
     }
 
+    #[inline]
+    fn sort(items: &mut [Self]) {
+        items.sort_by_key(|item| item.sort_key());
+    }
+
     #[inline]
     fn batch_size(&self) -> usize {
         self.batch_size