fix(PolyDataMapper): Update VBO build time even when reusing VBO

This build time is used to check if rebuild is needed
This will avoid `getNeedToRebuildBufferObjects` to always return true
It didn't rebuild the VBO but entered `buildBufferObjects` because of that

Author: bruyeret

Sources/Rendering/OpenGL/PolyDataMapper/index.js

@@ -1947,9 +1947,9 @@ function vtkOpenGLPolyDataMapper(publicAPI, model) {
         publicAPI.updateMaximumPointCellIds();
       }
 
-      model.VBOBuildTime.modified();
       model.VBOBuildString = toString;
     }
+    model.VBOBuildTime.modified();
   };
 
   publicAPI.getAllocatedGPUMemoryInBytes = () => {