Canvas: Change the node mask of the ODGauge camera

Since the Canvas cameras are no longer in the scene graph, we no longer
need to explicitly make them render only in the Classic pipeline's far
camera.

simgear/canvas/ODGauge.cxx

@@ -210,8 +210,7 @@ namespace canvas
   //----------------------------------------------------------------------------
   void ODGauge::setRender(bool render)
   {
-    // Only the far camera should trigger this texture to be rendered.
-    camera->setNodeMask(render ? simgear::BACKGROUND_BIT : 0);
+    camera->setNodeMask(render ? 0xffffffff : 0);
   }
 
   //----------------------------------------------------------------------------