Since Qt tests are currently Qt5-only don't build them for Qt6

Signed-off-by: Geoff Hutchison <geoff.hutchison@gmail.com>

Author: ghutchis

tests/CMakeLists.txt

@@ -35,12 +35,12 @@ mark_as_advanced(AVOGADRO_DATA_ROOT)
 # Add the tests for each module.
 add_subdirectory(core)
 add_subdirectory(io)
-if(USE_QT)
+if(USE_QT AND QT_VERSION EQUAL 5)
   add_subdirectory(qtgui)
 endif()
 if(USE_OPENGL)
   add_subdirectory(rendering)
-  if(USE_QT AND USE_VTK AND TEST_QTGL)
+  if(USE_QT AND USE_VTK AND TEST_QTGL AND QT_VERSION EQUAL 5)
     add_subdirectory(qtopengl)
   endif()
 endif()