ENH: Remove version check for <= 5

src/Cxx/RectilinearGrid/RectilinearGrid.cxx

src/Cxx/RectilinearGrid/RectilinearGridToTetrahedra.cxx

src/Cxx/RectilinearGrid/VisualizeRectilinearGrid.cxx

src/Cxx/StructuredGrid/BlankPoint.cxx

src/Cxx/StructuredGrid/StructuredGridOutline.cxx

src/Cxx/StructuredGrid/VisualizeStructuredGrid.cxx

src/Cxx/StructuredGrid/VisualizeStructuredGridCells.cxx

src/Cxx/Utilities/ArrayCalculator.cxx

src/Cxx/Utilities/ArrayWriter.cxx

src/Cxx/Utilities/ExtractArrayComponent.cxx

src/Cxx/Utilities/PCAStatistics.cxx

src/Cxx/Utilities/ShepardMethod.cxx