Prevent spawning multiple pinning popups on right click

The dismiss logic only checks for `ACTION_DOWN` events, but when the
user frequently right-clicks OR right-press-move-release, we get
multiple `ACTION_MOVE` events instead, which are ignored by the dismiss
logic of the previous popup instance.

Attached screen recordings to the bug.

Bug: 362475367
Flag: EXEMPT bugfix
Test: manual
Change-Id: I665c3127e4b449a8f4c71e443cc6ae07c1bf2794

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

@@ -91,6 +91,7 @@ public class TaskbarViewCallbacks {
     public View.OnTouchListener getTaskbarDividerRightClickListener() {
         return (v, event) -> {
             if (event.isFromSource(InputDevice.SOURCE_MOUSE)
+                    && event.getAction() == MotionEvent.ACTION_DOWN
                     && event.getButtonState() == MotionEvent.BUTTON_SECONDARY) {
                 mControllers.taskbarPinningController.showPinningView(v, getDividerCenterX());
                 return true;