COMP: Remove unused variable in vtkRAdapter::RToVTKTree

The "maxWeight" variable is not used, so remove it.

Change-Id: I44ae769ed04e03d6a127180271f143411e8d0d7b
Merge topic 'vtkFiltersStatisticsGnuR-unused-variable' into master

9ec5f55d COMP: Remove unused variable in vtkRAdapter::RToVTKTree