Android: Make QtWindow package private

Pick-to: 6.7
Change-Id: I0231193c3118619b4d2fc9f4e7f0f85ddd0b41b8
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/android/jar/src/org/qtproject/qt/android/QtWindow.java

@@ -13,7 +13,7 @@ import android.view.ViewGroup;
 
 import java.util.HashMap;
 
-public class QtWindow extends QtLayout implements QtSurfaceInterface {
+class QtWindow extends QtLayout implements QtSurfaceInterface {
     private final static String TAG = "QtWindow";
 
     private View m_surfaceContainer;