add maybe unused

Author: ArchiePayne

vtkext/private/module/vtkF3DRenderer.h

@@ -556,7 +556,7 @@ class vtkF3DRenderer : public vtkOpenGLRenderer
   bool GridVisible = false;
   bool GridAbsolute = false;
   bool AxisVisible = false;
-  bool AxesGridVisible = false;
+  [[maybe_unused]] bool AxesGridVisible = false;
   std::optional<bool> EdgeVisible;
   bool TimerVisible = false;
   bool FilenameVisible = false;