Add comment regarding Overview TaskViews

Just adds a comment explaining the elevation of Overview TaskViews. No code changes.

Bug: 208650434
Test: None needed.
Change-Id: I19c434f8473237a4a0f6fe36deecc9c80e7b8a49
diff --git a/quickstep/src/com/android/quickstep/views/RecentsView.java b/quickstep/src/com/android/quickstep/views/RecentsView.java
index dc886f6..b276478 100644
--- a/quickstep/src/com/android/quickstep/views/RecentsView.java
+++ b/quickstep/src/com/android/quickstep/views/RecentsView.java
@@ -3107,7 +3107,9 @@
             anim.addOnFrameCallback(this::updateCurveProperties);
         }
 
-        // Add a tiny bit of translation Z, so that it draws on top of other views
+        // Add a tiny bit of translation Z, so that it draws on top of other views. This is relevant
+        // (e.g.) when we dismiss a task by sliding it upward: if there is a row of icons above, we
+        // want the dragged task to stay above all other views.
         if (animateTaskView) {
             dismissedTaskView.setTranslationZ(0.1f);
         }