Misc. typo fixes

Common/DataModel/vtkGenericCellTessellator.h

Common/DataModel/vtkSimpleCellTessellator.h

Filters/Core/vtkDelaunay2D.cxx

Filters/Core/vtkVoronoi2D.h

Filters/Extraction/vtkExtractCellsByType.h

Filters/General/vtkEdgePoints.cxx

Filters/Geometry/vtkStructuredAMRGridConnectivity.cxx

Filters/Geometry/vtkStructuredAMRGridConnectivity.h

Filters/Geometry/vtkStructuredGridConnectivity.cxx

Filters/Points/vtkConnectedPointsFilter.h

Filters/Points/vtkEllipsoidalGaussianKernel.h

Imaging/Hybrid/vtkCheckerboardSplatter.h

Rendering/ContextOpenGL2/vtkOpenGLContextDevice2D.h