Fix typo introduced by commit 8d376ed

Co-authored-by: Steve Pieper <pieper@bwh.harvard.edu>

Libs/Visualization/VTK/Core/CMakeLists.txt

@@ -65,7 +65,7 @@ if(CTK_LIB_Scripting/Python/Core AND CTK_LIB_Scripting/Python/Core_PYTHONQT_USE_
 endif()
 
 if(CTK_LIB_Scripting/Python/Core AND CTK_LIB_Scripting/Python/Core_PYTHONQT_USE_VTK)
-  include(
+  include_directories(
     ${PYTHON_INCLUDE_DIRS}
     ${PYTHONQT_INCLUDE_DIR}
     )