Remove EdgeFlags test from OpenGL2
Remove EdgeFlags test from OpenGL2

Edge visibility (on/off per edge) via vtkDataSetAttributes::EDGEFLAG is not
supported. It was “free” in the old backend (glEdgeFlag) but in newer GL the
function is gone.  Not worth implementing as it is complex to code.

Change-Id: I1736063bf032b383863ae09e40f88766eb602bc9

ashray/VTK-EVM,sumedhasingla/VTK,SimVascular/VTK,johnkit/vtk-dev,candy7393/VTK,sankhesh/VTK,sumedhasingla/VTK,gram526/VTK,sumedhasingla/VTK,candy7393/VTK,keithroe/vtkoptix,msmolens/VTK,hendradarwin/VTK,candy7393/VTK,mspark93/VTK,sankhesh/VTK,demarle/VTK,ashray/VTK-EVM,candy7393/VTK,mspark93/VTK,johnkit/vtk-dev,gram526/VTK,msmolens/VTK,msmolens/VTK,keithroe/vtkoptix,SimVascular/VTK,SimVascular/VTK,sankhesh/VTK,sankhesh/VTK,demarle/VTK,sumedhasingla/VTK,gram526/VTK,johnkit/vtk-dev,keithroe/vtkoptix,jmerkow/VTK,jmerkow/VTK,johnkit/vtk-dev,ashray/VTK-EVM,sumedhasingla/VTK,SimVascular/VTK,jmerkow/VTK,ashray/VTK-EVM,candy7393/VTK,mspark93/VTK,keithroe/vtkoptix,sumedhasingla/VTK,jmerkow/VTK,keithroe/vtkoptix,candy7393/VTK,gram526/VTK,keithroe/vtkoptix,sumedhasingla/VTK,SimVascular/VTK,gram526/VTK,ashray/VTK-EVM,sumedhasingla/VTK,jmerkow/VTK,demarle/VTK,keithroe/vtkoptix,gram526/VTK,demarle/VTK,gram526/VTK,SimVascular/VTK,demarle/VTK,candy7393/VTK,sankhesh/VTK,sankhesh/VTK,hendradarwin/VTK,msmolens/VTK,jmerkow/VTK,demarle/VTK,hendradarwin/VTK,msmolens/VTK,SimVascular/VTK,demarle/VTK,sankhesh/VTK,msmolens/VTK,sankhesh/VTK,johnkit/vtk-dev,mspark93/VTK,mspark93/VTK,ashray/VTK-EVM,ashray/VTK-EVM,hendradarwin/VTK,candy7393/VTK,jmerkow/VTK,msmolens/VTK,ashray/VTK-EVM,gram526/VTK,johnkit/vtk-dev,mspark93/VTK,mspark93/VTK,hendradarwin/VTK,mspark93/VTK,jmerkow/VTK,SimVascular/VTK,johnkit/vtk-dev,msmolens/VTK,demarle/VTK,hendradarwin/VTK,keithroe/vtkoptix,hendradarwin/VTK