Remove QQuickWindow::glslVersion & glslIsCoreProfile

Superceded by the OpenGLInfo attached type
=> remove the API before it gets released

Change-Id: I7511fd28eb375eb3cd3cdd4bda6d82c1883e3094
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>