Tweak logic specifying libraries to link against VisualizationVTKCore

Since vtkRenderingFreeTypeOpenGL2 does not exist and vtkRenderingFreeTypeOpenGL, the
suffix OpenGL is hardcoded. Also move the logic in the FontConfig block.

Worth noting that vtkRenderingFreeTypeOpenGL has been removed in
version > 6.2.0 (See kitware/VTK@4f7460a5)

Libs/Visualization/VTK/Core/CMakeLists.txt

@@ -73,9 +73,6 @@ if(${VTK_VERSION_MAJOR} GREATER 5)
     vtkRenderingAnnotation
     vtkRenderingCore
     )
-  if(TARGET vtkRenderingFreeType${VTK_RENDERING_BACKEND})
-    list(APPEND VTK_LIBRARIES vtkRenderingFreeType${VTK_RENDERING_BACKEND})
-  endif()
   if(TARGET vtkRendering${VTK_RENDERING_BACKEND})
     list(APPEND VTK_LIBRARIES vtkRendering${VTK_RENDERING_BACKEND})
   endif()
@@ -91,6 +88,10 @@ if(${VTK_VERSION_MAJOR} GREATER 5)
   if (TARGET vtkRenderingFreeTypeFontConfig AND UNIX AND NOT APPLE)
     find_package(FontConfig QUIET)
     if (FONTCONFIG_FOUND)
+      # With VTK > 6.2.0 (commit 4f7460a5), vtkRenderingFreeTypeOpenGL has been removed.
+      if(TARGET vtkRenderingFreeTypeOpenGL)
+        list(APPEND VTK_LIBRARIES vtkRenderingFreeTypeOpenGL)
+      endif()
       list(APPEND VTK_LIBRARIES
         vtkRenderingFreeTypeFontConfig
         )