Fix the build without wayland/kwayland

This fixes the build of plasma-framework on KDE CI. Without this it will
error out as,

dialog.cpp(309): error C2065: 'shellSurface': undeclared identifier
dialog.cpp(310): error C2065: 'shellSurface': undeclared identifier
dialog.cpp(310): error C2227: left of '->setPosition' must point to
class/struct/union/generic type

Signed-off-by: Bhushan Shah <bhush94@gmail.com>

src/plasmaquick/dialog.cpp

@@ -304,11 +304,13 @@ void DialogPrivate::updateVisibility(bool visible)
                 updateLayoutParameters();
             }
 
+#ifdef HAVE_KWAYLAND
             //if is a wayland window that was hidden, we need
             //to set its position again as there won't be any move event to sync QWindow::position and shellsurface::position
             if (shellSurface) {
                 shellSurface->setPosition(q->position());
             }
+#endif
         }
     }