improve axes labels a bit under ray tracing
once enabled anywhere axes labels were always drawn with ray tracers. This prevents that.
note: the root cause of this and other widget problems is that VTK/Rendering/SceneGraph's build traversal lacks a place for custom composite actors and representations to exercise control over the children. That will take some thinking.
fixes: #20363 (closed)
Backport: release
Edited by David E. DeMarle