Revert "Remove popup container drag listener on close complete."

This reverts commit 1f7afc7740.

Reason for revert: Not all activity contexts have a drag controller, so this will cause a crash within those (e.g. SecondaryDisplayLauncher).

Change-Id: Idf7c880d8213951d06fecc3fb8cf6e8efd2037b0

src/com/android/launcher3/popup/PopupContainerWithArrow.java

@@ -508,7 +508,6 @@ public class PopupContainerWithArrow<T extends Context & ActivityContext>
     @Override
     protected void closeComplete() {
         super.closeComplete();
-        mActivityContext.getDragController().removeDragListener(this);
         PopupContainerWithArrow openPopup = getOpen(mActivityContext);
         if (openPopup == null || openPopup.mOriginalIcon != mOriginalIcon) {
             mOriginalIcon.setTextVisibility(mOriginalIcon.shouldTextBeVisible());