Fix PhysicalBone gizmo not showing

The new CollisionObject gizmo used for custom shapes was used with
higher priority due to alphabetical order and was preventing physical
bones from being displayed in the editor.

editor/node_3d_editor_gizmos.cpp

@@ -3531,7 +3531,7 @@ String CollisionObject3DGizmoPlugin::get_gizmo_name() const {
 }
 
 int CollisionObject3DGizmoPlugin::get_priority() const {
-	return -1;
+	return -2;
 }
 
 void CollisionObject3DGizmoPlugin::redraw(EditorNode3DGizmo *p_gizmo) {