Fix a few regressions related to the flicker fix (#9190)

This pull request fixes
https://github.com/zed-industries/zed/issues/9187 and fixes also ix a
rendering problem that would show cursors on the same plane:


![image](https://github.com/zed-industries/zed/assets/482957/208304a4-286a-4fd9-a3d8-e2913e3a3dc7)


Release Notes:

- N/A

crates/editor/src/element.rs

@@ -2083,11 +2083,9 @@ impl EditorElement {
     }
 
     fn paint_cursors(&mut self, layout: &mut EditorLayout, cx: &mut ElementContext) {
-        cx.paint_layer(layout.text_hitbox.bounds, |cx| {
-            for cursor in &mut layout.cursors {
-                cursor.paint(layout.content_origin, cx);
-            }
-        });
+        for cursor in &mut layout.cursors {
+            cursor.paint(layout.content_origin, cx);
+        }
     }
 
     fn paint_scrollbar(&mut self, layout: &mut EditorLayout, cx: &mut ElementContext) {