Set Paraview rendering backend to OpenGL2

Projects/paraview.cmake

@@ -48,6 +48,7 @@ add_external_project(paraview
     -DPARAVIEW_CLIENT_RENDER_SERVER_TESTS:BOOL=FALSE
     -DPARAVIEW_COLLABORATION_TESTING:BOOL=FALSE
     -DVTK_BUILD_QT_DESIGNER_PLUGIN:BOOL=FALSE
+    -DVTK_RENDERING_BACKEND:STRING=OpenGL2
 
     -DPARAVIEW_BUILD_PLUGIN_PythonQtPlugin:BOOL=TRUE
     -DPYTHONQT_DIR:PATH=<INSTALL_DIR>