LegendGridActor: expose new properties

Display new properties of Legend Grid.

Updates VTK with the following commits:

• Louis Gombert: legend-scale-grid (vtk/vtk!10869 (merged))
• Christos Tsolakis: restrict-readthedocs-job (vtk/vtk!10880 (merged))
• Jaswant Panchumarti (Kitware): fix-num-contour-return-type (vtk/vtk!10821 (merged))
• Ben Boeckel: vtkParseDependencyTracking-path-escaped-chars (vtk/vtk!10875 (merged))
• Nicolas Vuaille: LegendScaleOrigin (vtk/vtk!10867 (merged))