Remove View::minimumSizeHint()

It's a QWidget specific concept, so move it to the qtwidgets
frontendcode. QtQuick won't need it.

src/qtquick/views/ViewWrapper_qtquick.cpp

@@ -230,3 +230,8 @@ bool ViewWrapper_qtquick::testAttribute(Qt::WidgetAttribute) const
 void ViewWrapper_qtquick::setCursor(Qt::CursorShape)
 {
 }
+
+QSize ViewWrapper_qtquick::minSize() const
+{
+    return {};
+}