Add doc clarifying Taskabr icon alpha consumer purpose.

The motivation ternary `alpha > 0 ? 0 : 1` was not immediately clear, so adding some clarification for future readers.

Test: No
Change-Id: I558e86153e68572a519317dba7fbba180cb5678e
Fix: 239074423

quickstep/src/com/android/launcher3/taskbar/TaskbarLauncherStateController.java

@@ -95,6 +95,10 @@ import java.util.function.Supplier;
     private boolean mCanSyncViews;
 
     private final Consumer<Float> mIconAlphaForHomeConsumer = alpha -> {
+        /*
+         * Hide Launcher Hotseat icons when Taskbar icons have opacity. Both icon sets
+         * should not be visible at the same time.
+         */
         mLauncher.getHotseat().setIconsAlpha(alpha > 0 ? 0 : 1);
         mLauncher.getHotseat().setQsbAlpha(
                 mLauncher.getDeviceProfile().isQsbInline && alpha > 0 ? 0 : 1);